Michael Gove has suggested the Conservatives should give Theresa May "maximum freedom of manoeuvre" by dropping the party pledge to not raise certain taxes.
The Conservative former cabinet heavyweight said the Prime Minister needs a "free hand" when it comes to the economy following the party's 2015 manifesto "tax lock" pledge, which states they would not raise income tax, VAT or national insurance.
Chancellor Philip Hammond was forced into a humiliating U-turn shortly after last month's Budget when a revolt from backbench Tory MPs forced him to ditch planned national insurance changes for the self-employed.
Mrs May has so far refused to repeat the "tax lock" pledge while Mr Hammond said he needed more "flexibility" in managing the economy, prompting Labour to claim the Conservatives are planning a "tax bombshell" should they retain power after the general election.
Asked if a commitment similar to the previous tax lock needs to be made in the Tory manifesto, Mr Gove told ITV 1's Peston On Sunday: "If I were the Prime Minister or Chancellor or advising them, I would want to have the maximum freedom of manoeuvre on that because I think in dealing with the deficit and in making sure we have economic confidence in this country, I think we need to have a free hand.
"But there's another point as well, which is both Theresa and Philip Hammond came into politics with the intention of bringing taxes down over time - particularly on the backbone on people on average and below average incomes."
Work and Pensions Secretary Damian Green, challenged following Mr Gove's remarks, told the same programme: "I'm not going to leak parts of the manifesto.
"My own personal view is people should make up their own mind on what parties have done as much as parties promise in manifestos, and we have a record as a party over decades of cutting taxes and wanting to keep taxes low."
Mr Green also confirmed the Tory manifesto will include a policy to cap energy bills.
This comes as the Sunday Times reports that Mrs May will try to reduce them by around £100 a year for an average family by capping gas and electricity bills for households paying standard variable tariffs.
Mr Green said: "I think people feel some of the big energy companies have taken advantage of them with the tariffs they've got."
He said it differed to a previous policy to freeze bills from former Labour leader Ed Miliband at the 2015 general election.
He added: "The difference is that we would have Ofgem setting a limit so it would be a cap, more flexible, be able to reflect market conditions so the market would still have an influence.
"That would mean, in practical terms, if the oil price fell again then consumers would benefit in a way they wouldn't have done under Ed Miliband's proposal."