Chancellor Rachel Reeves has defended a decision to reject compensation for women hit by changes to the state pension age after a backlash.
She said "the vast majority" of women knew the changes were coming, and "as Chancellor I have to account for every penny of taxpayers money spent".
However, politicians have called for the government to backtrack on the decision, with Labour MP Brian Leishman saying he was "appalled".
Campaigners say that 3.6 million women born in the 1950s were not properly informed of the rise in state pension age to bring them into line with men.
"We're certainly not giving up the fight," said Debbie de Spon, membership director of the Women Against State Pension Inequality (Waspi) campaign.
Ms Reeves said she understood that campaigners "feel disappointed by this decision", but recommendations by a parliamentary ombudsman had said that "around 90% of women did know that these changes were coming".
"I didn't judge that it would be the best use of taxpayers' money to pay an expensive compensation bill for something that most people knew was happening," she added.
Ms de Spon told the BBC Radio Four Today programme that the government's decision was "very disappointing" and that many of members of the Labour Cabinet had been "very supportive of Waspi" over the years.
"We think it's time we called in some of that support," she said.
Nine months ago, a parliamentary ombudsman had recommended compensation of between £1,000 and £2,950 for each of those affected, after a six year investigation.
Ms de Spon said: "It makes rather a mockery of that system if the [government] can cherry-pick which parts of that investigation they choose to accept."
The Liberal Democrats had earlier said the stance "sets an extremely worrying precedent" in its rejection of the ombudsman's findings.
However, the government has said compensation could cost up to £10.5bn.
Prime Minister Sir Keir Starmer said that would "impose a further burden on the taxpayer".
But Ms De Spon said former Conservative Chancellor, George Osbourne had saved more than £180bn by raising the state pension age and "boasted that it was easiest money he had ever saved".
"We're asking for a tiny fraction of that back as compensation for government failure," she said.