David Cameron said the state pension will continue to rise by at least 2.5% a year until 2020 if his party wins the General Election in 2015.
He promised to keep the "triple lock" system, which sees the state pension increase by the highest of inflation, wages or 2.5%.
"I want people when they reach retirement to know that they can have dignity and security in their old age," he told the BBC.
"People who have worked hard, who have done the right thing, who have provided for their families, they should then know they will get a decent state pension and they don't have to worry about it lagging behind prices or earnings and I think that's the right choice for the country."
Responding to Cameron's comments, the Liberal Democrats and Labour both said they support the triple lock in principle but have stopped short of following the Conservatives' pledge should either win power.
Meanwhile, former Labour minister Frank Field warned taxes would have to rise to pay for the Prime Minister's "triple-lock" pledge.
"If you are promising one group - a group that is more certain to vote – that they will get the gravy first, you are saying to others there is less for you... and somebody is going to have to pay the taxes to foot that bill," he explained.
He also said it was unfair for retirees to benefit while the rest of society are forced "to make sacrifices".
He added: "Younger families, with children, who are hungry deserve a similar amount of dignity, particularly if they are working."
However, Cameron insisted that ensuring pensions continue to rise while benefits for younger people are being cut was "fair".