Fifteen former Labour MPs will use an advertising bombardment on the eve of polling day to urge voters not to back current leader Jeremy Corbyn for prime minister.
The critics of Corbyn's leadership have signed a full-page advert due to appear in a number of local newspapers across Labour's heartlands in the north of England, targeting "dozens" of marginal constituencies, they said.
The advert, organised by anti-extremism campaign group Mainstream, states, "Everyone wants a safer, fairer society. But in this election the Labour Party is set to deliver the opposite.
"We were all lifelong Labour voters and all former Labour MPs. We are voting for different parties at this election, but we have all come to the difficult decision not to vote Labour."
It is not the first time Ian Austin, leader of Mainstream and one of the ringleaders behind the move, has called on voters to defeat Corbyn's Labour at Thursday's General Election.
Using Conservative Party campaign cash, the former Dudley North MP wrote to voters in marginal seats earlier this month urging them to support Boris Johnson for prime minister.
The former minister has been joined in backing Wednesday's advertising blitz by the likes of Dame Louise Ellman, the ex-Liverpool Riverside MP who resigned in October over Labour's record on dealing with anti-Semitism in its ranks, and Vote Leave chairwoman Gisela Stuart, who last month appeared alongside Johnson to endorse him at a Tory election rally.
Other signatories include those who walked out of Labour to form Change UK in February - Ann Coffey, Mike Gapes, Chris Leslie, Joan Ryan and Gavin Shuker - as well as former Lewisham West and Penge MP Jim Dowd and Liberal Democrat defector Rob Flello.
Tom Harris, an MP of 14 years, ex-High Peak MP Tom Levitt, Ivan Lewis, Michael McCann and John Woodcock make up the rest of the 15 Corbyn critics.
Austin, a former Gordon Brown ally, said it would be a "disaster" for the country if voters put Corbyn into Downing Street.
"This is a hard decision for Labour supporters to make," he said.
"It was extremely difficult for me and the other former Labour MPs involved too. But the risk is just too great.
"If Jeremy Corbyn enters Downing Street on Friday, it would be a disaster for the United Kingdom."
Austin said the Labour Party under Jeremy Corbyn had changed beyond recognition and no longer resembled the party he and millions of other Labour voters supported all their lives.
Australian Associated Press