Sinn Féin has said the Northern Ireland Office is a block to progress, and ought to be restrained by Mr Tony Blair.
The party intensified its criticism of the NIO in a speech by its chairman, Mr Mitchel McLaughlin, at a commemoration in Co Mayo yesterday.
The criticisms come as Sinn Féin sets out its stall before the resumption of talks this week, and after a fresh call by the Catholic Primate, Archbishop Seán Brady, for the IRA to stand down.
Sinn Féin, arguing for an irreversible process of political change, has insisted that unionist commitments to work the institutions of the Belfast Agreement must be matched by progress on demilitarisation, human rights and the equality agenda.
Earlier this month, Mr Gerry Adams, writing in The Irish Times, said the transfer of policing and justice powers could "form the spine" of a new political arrangement involving Sinn Féin and the DUP.
Mr McLaughlin's speech yesterday appears to add to the Sinn Féin list by calling on the British government to address the question of the NIO.
"The NIO, with its in-built unionist bias, runs the six counties virtually as the old Stormont government," he said at a ceremony to remember IRA hunger striker Michael Gaughan, who died 30 years ago.
Speaking in Ballina, Co Mayo, he accused the NIO of political bias, and of exerting undue political influence.
"Direct rule ministers fly in for a few hours a week simply to rubber stamp decisions pre-formulated by senior civil servants," said Mr McLaughlin.
"Too often those who work within and for the NIO demonstrate an unapologetic devotion to the unionist cause. The manifestation of unionist government for the unionist people is still preserved.
"Small wonder then that unionists generally are in favour of the status quo, no matter how undemocratic, so long as it poses no threat to their interests.
"Tony Blair needs to rein in the NIO. It is only as locally-mandated ministers that we will be able to remove the influence of the rejectionists and the securocrats in the NIO over every facet of our lives."
The tenth anniversary of the first IRA ceasefire falls tomorrow, the eve of the resumption of talks between the parties and the two governments at Stormont.
Addressing the question of that anniversary, the Police Service of Northern Ireland Chief Constable, Mr Hugh Orde, yesterday told the BBC he was convinced the IRA retained a capacity to return to violence but had no intention of doing so.
Archbishop Brady encouraged all sides to work for a settlement. "This means being willing to make the first move, not out of a position of weakness, but as an expression of self-confidence and the willingness to inspire self-confidence in others."
Referring to the IRA, he added: "An example would be a decision by the IRA to remove from the present political climate what has been called the 'excuse' of their continued existence."
Mr Martin McGuinness, Sinn Féin's chief negotiator, said: "\ are not under any illusions whatsoever about the implications of political progress and working institutions which are power-sharing and all-Ireland.
"What we have tried to do is show people that this can be a pathway to what is a passionately held belief of ours - that there should be a united Ireland."