The British government will devolve powers over policing and justice to the Northern Assembly by 2008 even if there is no agreement from unionists, the Ulster Unionist Party leader said today.
Reg Empey said the proposal trampled on the democratic process after learning of the fall-back plan in a letter from Northern Secretary Peter Hain.
The note to the Assembly's Policing and Justice Committee warned justice and deputy justice ministers from both sides of the community could be appointed by March 2008.
Sinn Féin has called for powers to be devolved as the party considers whether to accept the Police Service of Northern Ireland.
Mr Empey said: "The Government has given Sinn Féin an undertaking that there will be devolution of policing and justice powers by 2008 and if there is any nonsense between the parties the Government will step in and make the appointments themselves.
"It is a complete negation of the democratic process, but my primary point is that the Democratic Unionist Party were saying devolution of policing and justice will not happen in a political lifetime but it is clear from that letter that it will happen."
The route to devolution was agreed by the Irish and British governments at St Andrews in Scotland this autumn.
A shadow Assembly is in operation and full powers are to be restored by March after Sinn Féin hold their Árd Fheis to rubber-stamp accepting policing structures.
Assembly elections will be held before a new government is formed headed by Democratic Unionist leader Ian Paisley and his deputy, Martin McGuinness from Sinn Féin.
Mr Hain's letter said: "If there was no successful selection of ministers within the timeframe set out by St Andrews the Government would take any necessary steps to ensure that the timescale for devolution was not delayed.
"This includes the appointment of a justice minister."
Yesterday, Sinn Féin announced it would hold an Árd Fheis by the end of January after negotiating on policing issues since before Christmas.
This would involve co-operating with police investigations, sitting on police scrutiny bodies like the Policing Board and encouraging Catholics to join the force.
Democratic Unionist deputy leader Peter Robinson has given a guarded welcome to Sinn Féin's statement but said he would wait for republicans' actions before agreeing to share power.
He added there had been a "triple-lock" negotiated by his party ensuring no devolution of policing without unionist agreement.
Senior DUP figures including the Rev Willie McCrea MP, MEP Jim Allister and House of Lords peer Lord Morrow have expressed caution.