But Shadow Work and Pensions Secretary Rachel Reeves also said she wanted to see "a lot more detail" about the changes.
The comments came after the Opposition was criticised for a muddled response to George Osborne's Budget proposals, which would stop pensioners being forced to buy annuities and allow them to cash in funds.
Ed Miliband did not address the plans directly in the House, and senior figures such as former frontbencher Tom Watson have raised concerns about people blowing their retirement pots.
Speaking on BBC Radio 4's Any Questions last night, Ms Reeves said she did not believe the pensions and annuities markets were currently working well.
"I support reform and I support what has been announced this week, although we need to see a lot more detail about what that will mean in practice," she said.
"But I think we need wider reform."
Confirming that Labour would not seek to reverse the changes, Ms Reeves added: "I think the majority of people will not just draw down all their money.
"I think the majority of people will want to ensure that what they have saved will last them. Many people will still want to buy that annuity to get some security."
Mr Miliband said yesterday that Labour was "in favour of greater flexibility when it comes to pensions".
"There are certain questions that now need to be answered by this government about the fairness of these proposals," he said.
"Is it going to help all lower and middle income tax payers as well as those at the top of society?
"Is it going to ensure that those who want to buy an annuity - which is part of the current system - can do so, particularly if they are on low or modest income.
"And is the Government going to ensure that there is the right advice available to people?
"We're certainly not going to reject these proposals out of hand. That would be the wrong thing to do.
"These are complex proposals. We need to scrutinise the detail and we need to have some clear answers from the Government on some of those questions."