Sir Jeffrey Donaldson is "approaching his David Trimble moment" when he must face down opponents within his party in order to secure political progress, Lord Reg Empey has said.
The Ulster Unionist peer, who was a key ally of the late Lord Trimble as he sought the support of colleagues to share power at Stormont after the signing of the Good Friday Agreement, said the DUP leader and his assembly team "know the boycott isn't working" but that a number of the party's MPs were hindering progress.
Lord Empey's comments come days after an email emerged in which Sir Jeffrey rounded on internal critics.
The DUP leader famously walked out of the negotiations that led to the 1998 accord before quitting the Ulster Unionists in protest, throwing David Trimble's leadership into crisis.
In a message to party members last weekend, the Lagan Valley MP claimed some within his own ranks “manufacture” attacks that he said are “driven more by an effort to gain media coverage or advance their personal agenda than any desire to advance Northern Ireland”.
While the DUP leader has downplayed the significance of internal dissent, it is widely acknowledged that his party is divided over its response to the Windsor Framework.
Lord Nigel Dodds, who along with MPs Sammy Wilson and Ian Paisley is regarded as one of his party's hardliners, said last week that February's EU-UK breakthrough deal failed the DUP's seven tests, a statement seen as further limiting his leader's potential to compromise.
Lord Empey said that while he was in "no doubt" that without modification the protocol/Windsor Framework is "not good for Northern Ireland's long-term constitutional or economic position", he argued that circumstances had "transformed" since the DUP began its Stormont boycott last year.
The former UUP leader said he believed matters were coming to a head and that Sir Jeffrey was "approaching his David Trimble moment".
"I don't have any inside track on it but I think the evidence from his statement and other material that one picks up would lead one to believe that we're moving in that sort of direction," he said.
He said an intervention by the British government could avert a showdown but there were "elements who definitely feel that Stormont should not be restored".
"They see it as some kind of defeat and in those circumstances, once people get into these entrenched positions, it's very difficult to get out of them," he said.
