The Ulster Unionist leader has rejected a call from the party's sole MP to end its link with David Ervine's Progressive Unionist Party (PUP) because of its association with the UVF.
Lady Sylvia Hermon, MP for North Down, voiced her "distress" at Stormont two weeks ago at the decision of UUP Assembly members to permit Mr Ervine into their group.
Mr Ervine boosts the combined UUP-PUP voting bloc to 25 and would mean an extra unionist minister would be chosen in any restored Stormont executive under the d'Hondt mechanism for sharing out government departments.
Lady Sylvia said UVF refusal to contemplate weapons decommissioning before November at the earliest, and the alleged shooting of loyalist Mark Haddock by the UVF last week, meant that the link between the two parties was unsustainable.
However, Sir Reg Empey insisted it was the right policy and said he would stick by it despite Lady Sylvia's criticism.
"The problem of loyalist paramilitaries has evolved over 35 years and this exercise cannot be completed in the space of three weeks," he said. "There is progress to be made."
In the only note of concession to Lady Sylvia's concerns, he added: "Having said that, we will know relatively quickly whether those with whom we are engaged with are being disingenuous.
"If they are, then naturally the position will have to be reassessed, and I will not hesitate to do so."
In an interview in yesterday's News Letter the North Down MP stepped up her criticism of her party leader's tactic regarding Mr Ervine.
"Whilst I regarded our party's alignment with the PUP in the Assembly as a dangerously high-risk strategy - particularly after the UVF had issued one of its rare public statements warning that it would not decommission after November 24th - I did, nevertheless, think the link might just be worthwhile if it enabled Sir Reg Empey to hasten that decommissioning and prevent any more bloodshed.
"But that was three weeks ago. And what have we had since then? Any progress by the UVF towards decommissioning? Definitely not.
"On the contrary, we've had a restatement at the weekend of the UVF's position that it's not prepared to consider decommissioning prior to November. And heaped upon that has been the murder attempt on Mark Haddock."
Despite his defiant stance, Sir Reg said he respected Lady Sylvia's concerns.
"Fundamentally, though, it remains the right course of action and one which I, and others, are not prepared to walk away from.
"The rewards, if a meaningful transition can be secured, will be worth it."