More and more disillusioned Ulster Unionists will defect from the party if Mr David Trimble fails to quit as leader, the Rev Ian Paisley claimed tonight.
As the hardline Democratic Unionists swept to victory with 40 new seats on district councils across Northern Ireland, the North Antrim MP warned time was running out for his rival.
He said: "If his party sustains him they will be destroying themselves.
"They are already partially destroyed, and there are even councillors who have been elected just recently who are now making overtures to come over and join us."
After two days of counting, the DUP and Sinn Fein emerged as the big winners in the council polls to leave the state of the parties at:
- Ulster Unionists 154 seats
- Democratic Unionists 131 seats
- Social Democratic and Labour Party 117 seats
- Sinn Fein 108 seats
- Alliance 28
- Others 44
Despite remaining the largest local government party the UUP saw its seats drop by 31 from 185.
Close associates of Mr Trimble insisted the party's losses were not severe as they appeared, but Sinn Fein is poised to have its first ever Lord Mayor of Belfast after winning 14 seats at City Hall.
Councillors quitting over their opposition to the Good Friday Agreement and resignations meant only 168 UUP councillors contested the elections, Ulster Unionist Party aides claimed.
A spokesperson said the analysis of the 14 seats lost indicated approximately half had gone to anti-Agreement unionists and half to nationalists/republicans.
"Although the DUP have made some gains, they have mainly taken seats off other smaller parties and anti-Agreement candidates."
But the DUP wrested control away from the UUP in a number of councils, including Ards, Co Down and Ballymena, Co Antrim.
Massive gains were also made in Belfast, where the party had an extra three councillors elected, North Down and Newtownabbey.
Sinn Fein was the other big victor in the elections as party president Gerry Adams' fulfilled his prediction that it would smash the 100-seat barrier.
A total of 108 republican councillors were returned, including 14 in Belfast where Sinn Fein is now the largest single party, and set to have a member elected as Lord Mayor for the first time.
Despite the gains, not everything went according to plan for republicans however.
In Newry and Mourne Mr Conor Murphy, one of the party's most senior members failed to get elected even though he polled impressively in the Westminster election.
And in Derry City Council Mr Donncha MacNiallais, spokesman for the Bogside Residents Group which has been at the centre of protests over loyalist marches in the city mounted an unsuccessful bid.
Meanwhile the nationalist SDLP staved off heavy losses feared inside the party. They had 117 councillors elected - down just three from its 1997 total.
In Derry the party retained its 14 seats to remain the biggest group on the council.
Party leader Mr John Hume, under some pressure to stand down, insisted this was indicative of the solid vote for his party in both polls.
He said: "What has happened in this election is there has been an extra vote and most of it has gone to Sinn Fein."
A wide-ranging review of the party's electoral strategy and structures would now be carried out, Mr Hume said.
But he stressed any calls for him to resign must be decided by the SDLP rather than individuals.
PA