No side deals agreed - Villiers
No side deals have been agreed alongside the Stormont House Agreement aimed at breaking the stalemate in Northern Ireland, Theresa Villiers has said.
The Northern Ireland Secretary urged all sides to seize the chance offered by the agreement, reached after marathon talks just before Christmas, amid reports the Ulster Unionists are unhappy with the package.
In a Commons statement, Ms Villiers said the Government was prepared to try and pass Westminster legislation for the devolution of corporation tax to Northern Ireland, a key part of the agreement, before the General Election and told MPs she was "disappointed" Labour were being cautious about the plan.
Shadow Northern Ireland Secretary Ivan Lewis welcomed the agreement but said consultations on the impact of the corporation tax reforms should be completed without a rush to legislate.
The Stormont House Agreement, forged on December 23 after 11 weeks' discussions, has resolved destabilising wrangles over the administration's budget and its non-implementation of welfare reforms while establishing new structures to deal with the legacy of unsolved Troubles killings.
It achieved less progress on other vexed disputes over the flying of flags and parading, but did set out new processes to examine how to find solutions to those matters in the future.
Much of the plan has been facilitated with a £2 billion financial package from the UK government - an offer that combines some new money from the Treasury with enhanced borrowing access and flexibility.
Ms Villiers told MPs: "This agreement involves compromise on all sides and it has been widely welcomed. First Minister Peter Robinson hailed it as a monumental step forward for Northern Ireland, Deputy First Minister Martin McGuinness called it a remarkable achievement.
"But securing an agreement is not the end point - far from it. There is much work ahead on implementation for the Executive, for the UK Government and where appropriate for the Irish government as well.
"But I give this assurance: if the parties in the Executive press ahead on this, the Government will implement our side of the agreement and we will do it faithfully and fairly. There are no side deals."
She added: "In the Government's view, the Stormont House Agreement represents a genuine and significant step forward for Northern Ireland, offering the prospect of real progress on some of the most intractable issues faced there, problems which have defied multiple attempts to resolve them over the years.
"This agreement gives the five parties in the devolved Executive the chance to refocus and work together with renewed confidence for a more prosperous, more stable, more united and more secure future for the people of Northern Ireland.
"I urge them to seize the opportunities it presents to build a brighter future for Northern Ireland."
On Monday, Ulster Unionist Party (UUP) officers called for timely and transparent clarification of outstanding issues and voiced concern about the impact on public finances and side deals following the Stormont House Agreement negotiations.
It came as Mr Robinson accused Ms Villiers of breaking her word after she decided not to establish a panel to examine a parades dispute in Northern Ireland.
The UUP's ruling party executive claimed there had been poor financial management by the leadership of the five-party power-sharing administration.
A statement said: "It notes the Stormont House proposals of 23rd December 2014 and expresses severe reservations about the potential outworkings of the proposals.
"The proposals include many aspects of uncertainty. We call on the Northern Ireland Executive and Assembly to provide timely and transparent clarification on the issues."
On corporation tax, Ms Villiers said: "A Bill will be presented to the House shortly for first reading. If the Stormont parties press ahead with agreeing their final budget and on agreeing welfare reform legislation, the Government will use all its best endeavours to get the legislation on corporation tax on to the statute book before dissolution.
"The parties in Northern Ireland have made clear they believe corporation tax devolution can help them rebalance the economy and attract investment - not least because of Northern Ireland's unique position of having a land border with the Republic of Ireland.
"I welcome the fact it is this Government which is delivering this momentous and transformative change, subject to the important conditions contained in the agreement, and I call on the Opposition today to commit to supporting the Bill as a key part of the Stormont House Agreement."
Mr Lewis said Labour welcomed "many aspects" of the agreement and told MPs: "It isn't perfect but it's a genuine advance on the stalemate of the past two years."
But he said the Opposition wanted a slower process for working on corporation tax devolution.
Mr Lewis said: "We remain concerned at the Government's rush to introduce legislation on corporation tax devolution - a decision which will have profound implications for Northern Ireland and the rest of the United Kingdom.
"We believe there should be a proper consultation process including an analysis of the financial impact of significant reductions in corporation on Northern Ireland's block grant before introducing legislation in this House."
Ms Villiers said this position was "very disappointing".
She said: "I think this is a change which could have a significantly transformative effect on Northern Ireland's economy, I think it is in a unique position within the United Kingdom because it shares a land border with a jurisdiction with a much lower rate of corporation tax.
"I will continue to urge you to urge the shadow chancellor (Ed Balls) to allow Labour to support this change which I believe is good for Northern Ireland."
Ms Villiers was forced to defend David Cameron after he was accused by former Northern Ireland secretary Peter Hain of being less engaged with the province than any other prime minister for the last 20 years.
Mr Hain also said it was important that the issue of flags and parades does not get kicked into the long grass and warned that devolving corporation tax was not a "silver bullet" for the Northern Irish economy.
The senior Labour MP said: "Can I congratulate you and all the party leaders on reaching an agreement not least because many of us feared in view of the Prime Minister's astonishingly premature exit from the previous summit and his lack of engagement which has been greater in its lack of engagement than any prime minister for over 20 years.
"And on the key flashpoint issues of parades and flags how can you be sure that this won't be long grassed? That this process won't long grass these issues?
"And finally on corporation tax are you aware as Sir David Varney's report to the Treasury in 2007 which showed that 95% of businesses in Northern Ireland do not pay corporation tax?
"This is not a silver bullet, it will leave a £300 million hole, 3% of the block grant, if there's equalisation with the Republic of Ireland?"
Ms Villiers replied: "I can assure you that the Prime Minster has been closely engaged on this process and the visit he made along with the Taoseach I think was very significant in moving things forward and the financial package he was able to agree with the Treasury was a crucially important part of making the progress that we have.
"This Government has delivered these significant achievements on some of the most difficult issues that Northern Ireland faces and that is in large part due to the work that the Prime Minister has done."
Ms Villiers added that corporation tax on its own would not solve the problems in the economy but said it could have a transformative effect.
Meanwhile the DUP's Westminster leader Nigel Dodds said Ms Villiers had reneged on a promise to set up a panel to discuss controversial parades in North Belfast.
Mr Dodds said the decision would cause "immeasurable trouble".
He said: "But can you tell the House why eight days later on December 23 you went back on your word, you didn't consult the unionist parties, you didn't consult this House, you haven't made any further statement other than to retract and give to Sinn Fein the opportunity to announce that the panel wasn't going ahead, why did you do that?
"Is it not an act of gross bad faith? Is it not something that is gong to cause immeasurable trouble in the days, weeks and months ahead?
"Because the festering sore of the denial of human rights to the people of Twaddell isn't going to go away and if you don't intervene - it's your responsibility, it's not devolved - if you don't intervene and do something then it's going to get worse and worse in the weeks and months ahead."
Ms Villiers replied: "As we have had the chance to discuss the trouble was with the panel that it didn't have enough support - it never had nationalist support, the unionist coalition that had called for it to be set up in the first place couldn't produce a public statement in support, and had actually broken up because some of those smaller parties have walked out of it.
"None of the smaller parties were making the case for the panel publicly and there was a distinct lack of enthusiasm amongst those smaller parties."