UK Prime Minister Rishi Sunak on Monday dismissed rumours that he would quit before the July 4 general election, as criticism about his early departure from D-Day commemoration events rumbled on.

The Conservative leader issued an apology after outrage from veterans' groups that he declined to join other world leaders at an event in northern France to mark the 80th anniversary of the invasion.

His decision to instead record a television interview, which also prompted criticism from his own colleagues, was the latest misstep on the campaign trial for the vote.

But Sunak, whom opinion polls predict will lead the Tories to a shuddering defeat to the main opposition Labour party, was defiant. "People are gonna say what they're gonna say," he said.

He warned against thinking the election result was a foregone conclusion, and said he had battled back from adversity before, notably after an internal Tory leadership defeat to Liz Truss in 2022.

"The reality is I'm not going to stop going, I'm not going to stop fighting for people's votes, I'm not going to stop fighting for the future of our country," he added on a campaign stop.

Sunak had until January next year at the latest to call a general election but decided to do so early as inflation slowed, indicating a turnaround in the parlous state of the country's economy.

The announcement -- made during a downpour in Downing Street -- took his own party by surprise, sending it scrabbling to find candidates to stand in the 650 parliamentary seats up for grabs.

Other unforced errors before the D-Day decision included a campaign stop near where the Titanic was built, prompting comparisons of his leadership to the captain of a sinking ship.

Sunak, a 44-year-old former financier who has been prime minister since Truss's short-lived tenure, has also faced questions about the veracity of his repeated claims about Labour's personal tax plans.

He will likely face further scrutiny as the Tories, in power since 2010, publish their formal policy proposals on Tuesday.

Labour launches its manifesto on Thursday. Party leader Keir Starmer on Monday said there would be "no tax surprises" in it for working people.