Tory supporters have launched an extraordinary attack on former Prime Minister Liz Truss, despite concerns she will jeopardise Rishi Sunak's electoral prospects.
One said her ex-party leader should back the prime minister or'shut up', adding she had 'zero credibility'.
Sunak is hoping to use the event in Manchester to convince voters he is the man to solve the UK's problems. But senior Tories fear Ms. Truss will instead remind the public of the economic chaos that defined her less than two months in office.
Ms Truss will speak at a 'growth rally' at the conference to push Mr Sunak on tax cuts. The Great British Growth Rally, also known as the Great British Growth Rally, is planned to draw in a large crowd.
But Ms Truss' plans have triggered fury among senior Tories, coming as they do when the party is facing a potentially disastrous electoral defeat next year.
Sir Alan Duncan, the former prime minister, said: 'Liz Truss should back the prime minister or shut up.
Another Tory grandee said the party had already suffered at the polls from years of factions and lack of discipline and that for Ms Truss, as a former prime minister to take the stage advocating a different agenda to Mr Sunak, is total and utter disgrace. The tragedy is that even one member of parliament thinks she is worth listening to.
The row came as Sunak's latest relaunch failed to work, he added, appealing to core voters rather than 'expanding your appeal to other voters'.
One Tory official said that calls for Ms Truss to pipe down were 'naive optimism'.
The former prime minister, Boris Johnson, who has drawn attention away from his party leader in recent times, is not believed to be planning to attend the conference.
In 2018 after he resigned as foreign secretary over Brexit, Mr Johnson caused mayhem at the Tory conference, giving a crowd-pleasing speech to a capacity audience of 1,500, some of whom had queued for four hours to see him.
The Conservatives enter their last party conference before the election, knowing their path to retaining the keys to Downing Street is narrow.
The party has been trailing Labour in the polls month-on-month.
The Tories closed the gap slightly after last week's announcement on green legislation, including an extra five years before the phasing out of the purchase of new petrol and diesel cars.
But as the starting gun is fired on the race for power, Tory MPs are nervously watching Mr Sunak's performance this week.
The prime minister is widely expected to have been working on his speech to the conference for weeks.
Earlier this week, he attempted to play down the spectre of his predecessor by making fun of Ms Truss at a dinner with journalists.
I'm glad to see actually that Liz Truss has been quiet reflecting, he said. Who's to blame? What is the Treasury? I haven't thought of a [body] in British public life that hasn't yet been blamed.