The Ulster Unionists' sole MP has said she was unaware of moves to permit David Ervine to join the party's Assembly grouping and is "deeply distressed" by it.
Lady Sylvia Hermon told the House of Commons yesterday she was not a party to the decision which has highlighted some strains in the relationship between the MP and Sir Reg Empey, the party leader.
Mr Ervine leads the Progressive Unionist Party which is linked to the outlawed UVF, which does not have a ceasefire.
The last Independent Monitoring Commission report cited the UVF's many criminal and paramilitary activities and reported that the group was not considering an end to activity or the decommissioning of any weapons.
Mr Ervine signed on at the Assembly alongside the Ulster Unionists, in a move which would increase to three the number of ministerial positions it would receive if a power-sharing executive is formed.
He has defended the move on the grounds that it would mean seven unionist ministers to five nationalist - an outcome, he says, which would serve his constituents better.
The SDLP has condemned as hypocrites unionists who have refused to work with Sinn Féin on account of its association with the IRA.
Lady Hermon told MPs yesterday she had discussed the matter during a long telephone call with Sir Reg.
The North Down MP did not support Sir Reg for the leadership following David Trimble's resignation after last May's Westminster election.
"If Sir Reg is able to establish now a policy to bring about loyalist decommissioning and prevent any more murders, any more Lisa Dorrians in my constituency, then that would be worthwhile," she said in the Commons.
"Apart from that I am deeply distressed by my colleagues' decision," she added.