Up to 400,000 people will benefit immediately from the coalition's radical pensions shake-up, David Cameron has said.
The Prime Minister, who will attempt to capitalise on the positive reception for the changes today by meeting Saga members in Brighton, said they represented core Tory values.
Meanwhile, London Mayor Boris Johnson has hailed the policy as "Thatcherite" - but risked fuelling concerns about a housing market boom by saying "huge numbers" of people would now sink their retirement savings into property.
The interventions came after Labour said it supported the principles behind the surprise overhaul unveiled in George Osborne's Budget last week.
The Chancellor announced moves to scrap rules that force most pensioners to use their direct contribution funds to buy an annuity, even though the rates can be poor.
Although most of the reforms will apply from April next year, a number will be brought in from Thursday to ensure people close to retirement do not miss out.
Individuals with total pension savings of £30,000 or less will be able to take the full amount as a lump sum, nearly double the current £18,000 limit.
Speaking ahead of his visit, Mr Cameron said: "This is about our values. It's about backing those who work hard, save and do the right thing. And it's about saying that the best people to look after their money are those who earned it in the first place.
"Labour have been all over the place. First they come out with the patronising nonsense that people can't be trusted to spend their own money sensibly. Then they back our plans. Then they're not sure.
"So the contrast is clear: while Labour dither and flail around for ideas, we have made long-term changes that will give millions greater security in old age.
"Labour ignored Britain's savers, we are on their side. Labour punished those who work hard and play by the rules, we are on their side.
"This is an historic change - the biggest revolution in pensions and savings for 100 years - and I'm proud the Conservatives have delivered it."
In his regular Daily Telegraph column, Mr Johnson welcomed the package as a "grenade".
"The decision to make it possible for people to decide what to do with their own pension pot is Thatcherite in its elegance," he wrote.
"It is free market, it is libertarian, it is all about trusting people to run their own lives - and, as the wretched Labour party is finding out, it is very hard to disagree with."
He added: "I don't think many will end up blowing it on Italian cars, actually.
"I think the vast majority will want to put their pots into the market with the greatest yield in the last 40 years - and that is property; and I expect huge numbers of those approaching pensionable age will be thinking about how they - the baby-boomers - can do something to help the younger
generation with the single biggest problem they face, namely the cost of housing.
"This pensions change is not a social disaster, but a wonderful opportunity.
"It is a chance for the older generation to find that sudden wodge of dosh that will enable them to help their children or grandchildren find a deposit and get on the ladder; and the existence of those new deposits will give developers even greater confidence to build more homes - and faster than they are now.
"I am not saying all pensioners will follow such a path of enlightened self-interest; but large numbers will."
Mr Miliband was seen as having dodged taking a position on the issue in the Commons, and while some Labour MPs have since condemned the move, others have urged the leadership to support it.
Pressure mounted after two polls over the weekend suggested the Tories had effectively wiped out Labour's advantage.
Shadow work and pensions secretary Rachel Reeves insisted the party backed the shake-up in principle.
"We support reforms to the pension market, so people can get a better deal and have more flexibility, especially at the moment, when people are just not getting a very good deal on their annuity," she told Sky News' Murnaghan programme.
"We're talking about people here who are coming up to retirement, who have saved all their life, and put things aside.
"I think we can trust those people to make sensible decisions about how they want to support themselves in retirement."
Mrs Reeves argued that the Government had not "gone far enough" in the Budget, and should also impose a cap on fees and charges by pensions and annuities firms.
Acknowledging that some in her party had concerns about the plans, the MP said she wanted to be certain that the measures would "benefit people on modest incomes and not just the privileged few".
Shadow business secretary Chuka Umunna declined to say whether Labour would vote in favour of specific legislation.
"We need to see the Bill and I'm not going to sign a blank piece of paper," he told the BBC's Andrew Marr Show.
Shadow Treasury minister Chris Leslie also questioned whether Mr Osborne was merely trying to raise revenue.
"This is something the Chancellor has done, he claims, for reasons of freedom and flexibility but is it just a coincidence he is grabbing quite a lot of tax from pensioners early on to plug a hole which is necessary because the deficit has not gone down," he told the BBC's Sunday Politics.