David Cameron pledged to continue guaranteed rises in the basic state pension by retaining the "triple lock" system if the Conservatives win the 2015 general election.
The Prime Minister sought to reassure older voters that their payouts would continue to rise in line with the higher of inflation, wages or 2.5% at least until 2020.
OAPs face a post-election squeeze on benefits such as winter fuel payments, bus passes, TV licences and prescriptions as politicians seek to square continued spending restraint with an ageing population.
But Mr Cameron insisted that pensions would not be hit by continued austerity measures.
"A Conservative government will offer pensioners a more secure future by pledging today that we will carry on using the triple lock after the next election to protect the basic state pension," he said.
"We can only afford to do this because we are taking difficult decisions to cut the deficit and get spending under control as part of our long-term economic plan.
"I want to do everything we can to help people who have worked hard and done the right thing."
The basic state pension will be around £440 a year higher from April than if it had been uprated in line with average earnings since 2011-12, Downing Street said.
Mr Cameron has already indicated that the state pension would be the only spending exempt from a new cap on overall welfare spending.
Conservatives contrasted that with comments made by shadow work and pensions secretary Rachel Reeves that they would be included by Labour.
The Opposition subsequently said it was committed to the triple lock and that Ms Reeves had been speaking about long-term policy over the next 50 years.
Chancellor George Osborne warned in his Autumn Statement that the state pension system faced collapse without action to reduce the cost to taxpayers.
His solution was to tell m illions of people in their 30s and 40s they will have to wait until they are 68 or 69 before qualifying for a state pension.
That sparked union protests that young people were being expected to "work until they drop".
Mr Cameron has faced criticism - including from senior Tory cabinet colleagues - for making and sticking by a 2010 election promise not to cut OAP benefits.
Chancellor George Osborne has indicated they could be reviewed in the years after the election because ''we have got to look at how we can afford them''.
Labour has said it would strip winter fuel payments from the richest 5% of pensioners and the Liberal Democrats have also said they would means-test the benefits.
Lib Dem former cabinet minister Chris Huhne has accused politicians of "pandering" to the "selfish, short-sighted old" because they are the group most likely to vote.
Mr Cameron told the Sunday Times the pension pledge was "the first plank of the next general election manifesto.
"In a civilised society...knowing you're going to have a decent state pension...is, I think, a really powerful thing."
Defending the decision to raise the pension age, he said: "People aren't stupid - they know that you can only pay a decent state pension if you take tough, difficult, long-term decisions."
Liberal Democrat pensions minister Steve Webb said in June that, while he backed the continuation of the triple lock, parties would need to examine whether it remained affordable post-2015.
In his newspaper interview, Mr Cameron said he hoped to be able to offer tax cuts as the economy improved and left open the door to a further reduction in the top rate of income tax.
The Prime Minister faces calls from right-wing MPs to bring it down from 45p - despite the controversial move from 50p already exposing the party to Labour claims of offering tax cuts to millionaires.
That move had brought in extra revenue to the Treasury, he insisted, adding: "Tax rates should be set to raise money, not to send messages.
"I'm interested in making sure that the rich in this country pay a lot of tax, which they do - they are paying a bigger share...than they were.
"If people can bring forward arguments about how to maximise the revenue from the top rate of tax. I'm always interested to read them."
Shadow chief secretary to the Treasury Chris Leslie said: "While ordinary families are facing a cost-of-living crisis it seems David Cameron wants to give people earning over £150,000 yet another tax cut.
"Working people are on average £1,600 a year worse off since the Tories came to office. But once again this Prime Minister seems determined to be on the side of the privileged few."
Paul Green, from the over 50s-specialist Saga said: "David Cameron's commitment to the triple lock for the state pension will be warmly welcomed by British pensioners, giving them confidence that their lifetime of work will be properly valued by society."