Theresa May has refused to guarantee the triple lock on pensions will continue.
The Prime Minister did say that pensioner incomes would continue to rise under a Conservative government.
But this prompted accusations from SNP Westminster leader Angus Robertson that the Tories could not be trusted on pensions.
Speaking at Prime Minister’s Questions, Mr Robertson asked Mrs May to guarantee the triple lock for increases on the state pension.
Mrs May replied: “I’ve been very clear that under this Conservative government, we have seen pensioners benefit as a result of what we’ve done to the basic state pension to the tune of £1,250 a year.
“I am clear that under a Conservative government, pensioner incomes would continue to increase.”
The Prime Minister’s response prompted cries of “answer” from the opposition benches, with Mr Robertson saying: “I asked the Prime Minister a pretty simple question, it was a yes or a no, and the Prime Minister failed to answer.
“So pensioners right across this land are right to conclude that this Tory Prime Minister plans to ditch the triple lock on the state pension.
“Too many women already face pensions inequality, and the Tories now won’t even guarantee the pensions triple lock, and the only reason that they will not guarantee it is because they want to cut pensions.
“Is not the message to pensioners you cannot trust this Prime Minister, you cannot trust the Tories on your pension.”
Mrs May again defended the Conservative record in Government on pensioners, reiterating that pensioner incomes would continue to increase.
She added: “He talks about inequality for women.
“It’s the change in the structure of the state pension introduced by this Government that is going to improve the lot of women, female pensioners, in the future, that is going to be much better for them.
“But one thing that pensioners in Scotland will know, as other voters in Scotland will know, is that if they believe in the union, there’s only one way to vote and that’s to vote Conservative.”
The Prime Minister and other senior ministers have repeatedly failed to guarantee the future of the triple lock, which ensures pensions increase in line with wages, inflation or by 2.5% - whichever is highest.
Labour has committed to keeping the triple lock.