Conservatives have sought to damp down speculation they are planning tax rises if Theresa May is returned to power in the general election on June 8.
Chancellor Philip Hammond has hinted he would like to drop the party's 2015 manifesto pledge not to put up income tax, VAT or national insurance contributions (NICs) during the lifetime of the parliament.
Attending the spring meeting of the IMF in Washington, Mr Hammond - who was forced into a Budget U-turn after critics said his changes to NICs for the self-employed breached that commitment - said he needed more "flexibility" in managing the economy.
His comments were seized on by Labour, which accused the Tories of planning "a tax bombshell" while the Liberal Democrats suggested they would hit "white van man".
However, the Financial Times reported that aides to the Chancellor in Washington were insisting no decision had been taken on whether to drop the tax pledge from the Conservative manifesto for June's election.
The row came after Mrs May risked angering traditionalist Conservatives after she reaffirmed the Government's commitment to international aid spending while refusing to guarantee the "triple lock" for pensioners.
Her announcement, during a campaign visit to her Maidenhead constituency on Friday, that she would stick by David Cameron's commitment to spend 0.7% of GDP on international aid, was sharply criticised by some Tories.
Former party chairman Lord Tebbit told The Daily Telegraph: "It is a very bad start to the campaign to insist on increasing aid every year whilst there is not sufficient money for the NHS. It does not seem to make good politics to me."
Sir Gerald Howarth, a Conservative former defence minister who is standing down at the election, told the paper: "It is so immoral to be spending £13 billion on overseas aid.
"It is taxpayers' money when social care is under pressure, NHS is under pressure, schools are under pressure."
Labour and the Liberal Democrats, meanwhile, seized on Mrs May's refusal to say whether the Conservative manifesto would keep the triple lock, which guarantees the state pension increases each year by inflation, average earnings or 2.5% - whichever is highest.
The Prime Minister insisted the party had always been clear about the need to support people in old age and that pensioners were £1,250 a year better off as a result of actions taken by the Conservatives.
"What I would say to pensioners is, just look what the Conservatives in government have done," she said.
"We were very clear about the need to support people in their old age, and that's exactly what we've done."
However, the Liberal Democrats accused the Tories of "getting their betrayal in early" while Labour said they were abandoning the elderly.
Jeremy Corbyn, campaigning in the North West on Saturday, said Labour would be using its 500,000 strong grassroots membership - the largest of any of the main parties - to get its message out to voters.
"This election is not a foregone conclusion. Labour's campaigning is off to a flying start," he said.
"We're using our membership strength to put thousands of people on the streets, knocking on doors and handing out leaflets to take our message direct to voters."