Theresa May has refused to guarantee that income taxes would not rise under a Tory government after Foreign Secretary Boris Johnson and Defence Minister Michael Fallon both ruled out a tax increase for higher earners.

The prime minister insisted that Tory tax plans have not changed at a campaign event in West Yorkshire on 3 June. She told voters that it was her party's "firm intention to reduce taxes for ordinary working families."

"Our position on tax hasn't changed. We have set it out in the manifesto," May said. "What people will know when they go to vote on Thursday is that it is the Conservative party that always has been and is and always will be a low tax party."

She added that the Labour Party's manifesto plans would "cost ordinary working people."

May explained that the Conservatives plan to increase the amount people can earn without paying tax to £12,500 and raise the 40p tax threshold.

The Tories scrapped a previous manifesto pledge not to raise VAT and National Insurance contributions.

The prime minister's comments come after Sir Michael Fallon ruled out an income tax increase. Fallon told The Daily Telegraph that voting for the Conservative Party was the only way people could be sure their tax would not go up.

"You've seen our record. We're not in the business of punishing people for getting on, on the contrary we want people to keep more of their earnings," he said. "The only way they can be sure their taxes won't rise is to vote Conservative. We already know your tax will go up if you vote Labour on Thursday."

Theresa May election
Theresa May has refused to rule out an increase in income tax ahead of the UK General Election REUTERS

Foreign Secretary Boris Johnson also ruled out a rise on Friday (2 June), telling BBC Newsnight that the Tories had "absolutely no plan to do so. Our plans are to cut taxes. Labour's plans are to put them up."

Labour Party leader Jeremy Corbyn has promised to increase income tax on those earning more than £80,000, by having the 45p tax rate kick in for people earning this amount, rather than at the current £150,000. Corbyn accused the Conservative Party of being in "chaos" over their tax plans.

"One minister says they're going to give no more tax rises indeed possibly tax reductions for the very wealthiest, then they can't answer the question about tax rises for the rest of the population, then they can't answer the questions about funding social care," he told reporters while travelling up to Lincoln for a campaign event.

Boris Johnson Michael Fallon
Foreign Secretary Boris Johnson (left) and Defence Minister Michael Fallon (right) have both ruled out income tax increases REUTERS/Joshua Roberts