Theresa May is coming under pressure to spell out her plans for pensions, after failing to commit the Conservatives to preserving the “triple lock” guarantee after the general election.

The Prime Minister dodged a question on pensions at a campaign event where she committed the party to maintaining its controversial promise to spend 0.7% of national income on international aid.

Meanwhile, Chancellor Philip Hammond signalled that he wants the upcoming Tory manifesto to drop the party’s pledge from the 2015 election not to raise income tax, national insurance or VAT over the life of the next Parliament.

.@PHammondMP refused today to rule out raising VAT, income tax & gave no commitment to protect the pension triple lock. — John McDonnell MP (@johnmcdonnellMP) April 18, 2017

Speaking during a visit to the IMF in Washington DC, the Chancellor told the BBC: “All chancellors would prefer to have more flexibility in how they manage the economy and how they manage the overall tax burden down (rather) than having to have their hands constrained.

“But what we put in the manifesto will be decided in the next few days and we will publish that.”

Liberal Democrats accused the Conservatives of “getting their betrayal in early”, while Labour leader Jeremy Corbyn highlighted the contrast between Mrs May’s silence on pensions with his own party’s commitment to keep the triple lock, which guarantees payments will rise annually by the highest of inflation, average earnings or 2.5% each year.

Mrs May was asked during a visit to a factory in her Maidenhead constituency whether older people can expect to see their pensions continue to rise, if she wins the election, as they have done so far under Conservative-led administrations.

.@Theresa_May just refused to commit to keeping the Triple-Lock on state pensions. Labour will keep Triple-Lock and won't abandon pensioners pic.twitter.com/0VCjQRgXAL — Jeremy Corbyn MP (@jeremycorbyn) April 21, 2017

She replied: “What I would say to pensioners is, just look what the Conservatives in government have done. Pensioners today are £1,250 better off as a result of action that has been taken.

“We were very clear about the need to support people in their old age, and that’s exactly what we’ve done.”

The PM was more willing to make her position clear on aid, following calls from charities and philanthropist Bill Gates for her to continue meeting the United Nations target enshrined in law by her predecessor David Cameron.

“Let’s be clear, the 0.7% commitment remains and will remain,” said Mrs May.

Shadow chancellor John McDonnell said: “Theresa May’s refusal to commit the Tories to maintaining the pensions triple lock only further proves the Tories are abandoning older people. It’s now clear pensions protections are now in jeopardy.

“Labour will stand up for older people by maintaining the pensions triple lock and by keeping the winter fuel allowance and free bus passes so that the elderly can go about their lives with the dignity they deserve.”