David Cameron accused Labour of "scaring pensioners"
Conservative leader David Cameron has made a personal "pledge" to pensioners, promising to protect the winter fuel allowance and free bus passes.
In a webchat with Saga magazine, he said he wanted to make sure that people had "dignity and security in old age".
In his Budget, Chancellor Alistair Darling also said Labour would not cut the winter fuel payment, which is £250 for over 60s and £400 for over 80s.
The Lib Dems have said they would raise the minimum age for the benefit to 65.
The age limit is already due to rise to 65 by 2020 - alongside plans to raise the state pension age for women - but Lib Dem leader Nick Clegg says his party would introduce the change immediately if elected.
The Conservatives claim that a single pensioner on an average income will be more than £110 a year worse off because of "tricksy" changes in the Budget.
According to their calculations, next year's 2.5% rise in the basic state pension will be £59 less than if it had been increased in line with inflation, and pensioners will also lose out because of the freeze on income tax allowances.
"Who would ever have thought a Labour government would hurt pensioners in such a devious way?" Mr Cameron said.
Labour has claimed the Tories "repeatedly opposed the support we have given to pensioners" and accused them of actually opposing the introduction of the winter fuel allowance in the first place.
But Mr Cameron said: "They're going around scaring pensioners, telling you that the Conservatives are going to cut the winter fuel allowance, cut pension credit and end free bus travel and TV licences for over 75s.
"I can promise you, these are lies, lies, lies.
"You have my word. If we win the election, we will protect all of these things."
In his webchat with Saga, Mr Cameron restated his party's commitments to freezing council tax for two years and restoring the link between the state pension and earnings.
He added: "I understand many, many pensioners live on incredibly tight budgets and so increases in electricity prices, or gas prices, or council tax, put incredible pressure on.
"And what I want to see is the ability to give people the chance to have dignity and security in old age."
The pensioners' vote will be fiercely contested at the coming election, especially as older people tend to be more likely to turn out at the ballot box.
A spokesman for Mr Darling said Tory claims that pensioners would be worse off following the Budget were "nonsense".
"Because inflation was negative last September, the chancellor's decision to freeze the allowance and increase the basic state pension by 2.5% represented a real-terms benefit for pensioners.
"If the Tories want to propose a new way of setting personal allowances and pension rates to spend more this year, they need to just say that clearly. And then set out how they'd meet the price tag of several billion pounds."