Sinn Fein leader Gerry Adams has said the Northern Ireland political process faces its greatest challenge since the Good Friday Agreement negotiations.
He criticised DUP leader Peter Robinson for not showing enough progressive leadership and claimed anti-agreement unionists had been allowed to set the agenda, undermining the devolved power-sharing government at Stormont.
Sinn Fein and the DUP, the two largest parties in the mandatory coalition, have been at loggerheads over welfare reform and plans for a peace centre at the site of a former high security prison near Belfast.
Mr Adams told the BBC: "The crisis is clearly a political crisis but the fact is citizens need to have confidence in the political institutions and because one of the biggest parties, the biggest party in the Executive (DUP), is not committed to what it signed up to when it went into government with Sinn Fein and the other parties, that confidence is being eroded."
The Sinn Fein president accused unionists of failing to engage positively in political negotiations surrounding contentious flags, parades and dealing with the toxic legacy of thousands of deaths during the conflict.
Dialogue has been stalled in a unionist protest over the handling of a loyal order parade in North Belfast.
The Irish Government has said it hopes talks can resume next month. But Mr Adams, a member of the Irish Parliament for the border constituency of Louth, said the stance of unionists meant there was no likelihood of negotiations resuming.
The proposal to develop a peace centre at the Maze prison site near Lisburn, which is owned by the Executive, was envisaged in the Sinn Fein and DUP-agreed Programme for Government but was dramatically torpedoed last year when the unionists withdrew their support.
Mr Robinson said he was responding to victims' concerns about the potential of a centre at the former prison being turned into a "terrorist shrine".
That followed a summer of sectarian violence and efforts were made to resolve community tensions via five-party talks chaired by former US diplomat Dr Richard Haass which ended after Christmas without agreement.
Since then there have been intermittent leaders' discussions held against the backdrop of deadlock over welfare reform, which threatens to strip millions from budgets for public spending.
Sinn Fein is opposing the implementation of Westminster reforms known by some as the bedroom tax which the party fears will hit the least well off hard. The DUP opposed the measures but argues it has no choice but to introduce them after the Treasury threatened to dock £87 million from the amount by which it funds the devolved administration.
This week Roads Minister Danny Kennedy warned thousands of street lamps may go out this winter because there is not enough money to repair them.
DUP East Londonderry MP Gregory Campbell said: "This Gerry Adams contribution this morning is a smokescreen about the welfare reform issue.
"The money tap from London, the £10 billion subvention that we get from London, has been turned down, it has been reduced."
This week a charity became the latest victim of the deadlock at the heart of the Stormont Executive, after it failed to gain approval for fundraising open days near the former Maze prison site.
The Ulster Aviation Society (UAS) hoped to attract 8,000 people to see its collection of aircraft housed in old wartime hangars on Stormont-owned land close to the prison buildings, but its plan has been consumed by the bitter political row between the DUP and Sinn Fein over stalled proposals for a peace centre in the one-time paramilitary jail.
Sinn Fein has withheld approval for the two open-day events this month, claiming its stance is linked to a DUP decision to block public visits to the prison.
But the DUP has, in turn, accused the republican party of playing politics with a charity.