At their latest meeting in TV studios before the poll, the two men took turns to face an interviewer and then an audience, whose questions and responses underscored the everyday struggles of many in Britain and the mistrust of politicians.
With just over three weeks until an election, opinion polls suggest Labour will easily win. Sunak was booed and heckled over doctors' strikes, migration and his policy to introduce national service for young people.
Starmer was taken to task for what one audience member said was his avoidance of answering questions, and over his previous support of his predecessor, left-wing veteran Jeremy Corbyn.
Labour leader Keir Starmer was asked about his past support for leftist predecessor Jeremy Corbyn. (AP PHOTO)
A poll taken after the event in the northern English town of Grimsby said 64 per cent believed Starmer had won the event on Sky News.
Starmer told the audience that he would start implementing his policies from 'day one' if he won the election but shied away from answering whether he was being honest when in 2019 he said his left-wing predecessor, Jeremy Corbyn, should become prime minister.
"I want to get the place when I can roll up my sleeves and work with you ... to say the government is on your side," Starmer said to applause. "That will be a massive difference to the last 14 years."
Sunak was challenged over some of his policies, which audience members said had yet to solve their inability to get dentist appointments, reduce waiting lists in the National Health Service or stop the arrival of migrants in small boats.
"I know we've been through a tough time, of course we have ... it's been tough for all of you here tonight, all of you watching, but I do believe we have turned a corner and we've got a clear plan for the future," he said.
"I am going to keep fighting hard until the last day of this election."
The event came a day after Sunak unveiled 17 billion pounds ($A31 billion) of tax cuts in his governing party's manifesto, trying to convince voters that he had a plan to make them better off while Labour's policies are vague and ill-thought through.
He said again on Wednesday that a vote for Starmer was akin to writing him a blank cheque, repeating the contested accusation that a Labour government would increase taxes by more than 2000 pounds ($A3800). Starmer denied that was the case.
On Thursday, Labour will be try to set the story straight with its own manifesto, a document which sets out the policies the party will pursue in government, an agenda Starmer said would put wealth creation and economic growth at its heart.
Labour has repeatedly said it will stick to strict spending rules - a line Labour, traditionally seen as the party of tax and spend, has adopted not only to try to show it has changed since being led by Corbyn but also to challenge Conservative attacks that it will increase taxes.
But it was Corbyn who came back to haunt Starmer on Wednesday, when he was asked whether he believed what he said when in 2019 he said the veteran leftist would make a good prime minister and when he made 10 left-wing pledges to become Labour leader a year later, several of which he has since dropped.
"Have I changed my position on those pledges, yes I have," said Starmer. "I think this party should always put the country first."
