Britain's Defence Secretary Michael Fallon leaving 10 Downing Street | Daniel Leal-Olivas/AFP via Getty Images Senior Tory minister pledges to freeze income tax for the rich Theresa May refuses to rule out income tax rise, saying only that Conservatives are ‘low tax party.’

LONDON — Less than one week before the U.K. general election on June 8, Theresa May's Conservative Party pledged it would not raise income tax for high earners.

In an interview with the Daily Telegraph published Saturday, Defense Secretary Michael Fallon said voting Tory was "the only way" workers across the wage spectrum could be sure their tax level wouldn't increase.

Asked if high earners could be sure the Conservatives aren't lining up any tax hikes for them, Fallon said: “Yes. 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."

The new promise strikes a stark contrast with Jeremy Corbyn's Labour Party, which has promised to increase income tax on those earning more than £80,000 to help fund social services.

Fallon's suggestion goes beyond the pledge the Conservatives made in their manifesto, which only rules out increases to VAT but leaves out a freeze on National Insurance, which is effectively another income tax in the U.K.

National insurance, VAT and income tax were all part of the so-called "triple tax lock" of David Cameron's 2015 manifesto that May has now dropped.

When asked to clarify her party's stance at an event on Saturday, May refused to rule out a rise in income tax, saying only that the Conservatives were the "low tax party" and that it was her "firm intention" to reduce taxes for "ordinary working families."

"Our position on tax has not changed. We have set it out in the manifesto," the prime minister said, according to Sky News.

According to the latest polls, the Labour Party is closing the gap with the Conservatives, polling at 39 percent to the Tories' 42 percent.

This article has been updated with new information.