Sinn Fein will crank up the pressure on Northern Ireland's power-sharing government if there is no deal to devolve policing and justice powers, a senior republican signalled last night.

The party's National Chairman Declan Kearney stopped short of threatening the future of the Stormont administration, but accused unionists and the government of "playing fast and loose" with negotiations.

The party strategist said Prime Minister Gordon Brown and Secretary of State Shaun Woodward had failed to prevent Democratic Unionist Party (DUP) leader Peter Robinson creating obstacles to a deal.

Government has offered a package of nearly £1billion to fund the transfer, but the DUP has said it will not move until community confidence in the Assembly taking-on such sensitive powers is secured.

In an article to appear in the Republican newspaper An Phoblacht tomorrow, Mr Kearney writes: "Today, unionists can exercise power in the Six Counties only if they accept partnership and equality.

"And, if the DUP can't do partnership and equality, then it won't be doing government either.

"So, Robinson does have decisions to make."

Last week it emerged that Mr Brown had agreed to provide £20million for former Royal Ulster Constabulary part time reserve officers. The republicans branded the move a side-deal to "buy-off" the DUP.

Sinn Fein has also criticised Mr Robinson for demanding that before devolution, government must scrap the Parades Commission, which rules on loyal order parades and has long been criticised by unionists.

Mr Kearney said: "The DUP and NIO (Northern Ireland Office) have played fast and loose with these negotiations.

"Their introduction of the parades precondition may not necessarily mean they are opposed to the transfer of power - although it might.

"But it demonstrates they are considering the reckless scenario of pushing transfer of powers beyond next year's Westminster election.

"And the DUP may still plan to raise new and more preconditions."

He added: "It is likely, for different reasons, that the DUP, NIO, Woodward, and Brown are basing short-term, tactical expediency upon three mistaken assumptions:

"One: That Sinn Fein will be weakened the longer they can play out delivery of transfer of policing and justice powers.

"Two: That Sinn Fein has invested so much in the achievement of transfer, we will simply roll over.

"Three: That Sinn Fein is so committed to the political institutions we no longer possess, or will want to use any effective political leverage in this situation.

"They are codding themselves and no one else."

The senior republican said that in the past the Government had gone to great lengths to support the then under-pressure Ulster Unionist leader David Trimble when he faced a challenge from the DUP.

He said that now the DUP was the largest party and was under pressure from hard-line elements, government was trying to appease it.

The DUP lost votes in this year's European election to the hard-line Traditional Unionist Voice.

Mr Kearney said: "The NIO and DUP strategists ought to remember that election results bring their own dynamics and pressures."

He added: "The DUP's and British Government's short-term expediency has all the potential to push this impasse into complete free-fall - they still aren't learning the political lessons.