Steve Webb wants to end the "lottery" in which many pensioners are trapped in potentially poor-value schemes until they die.
The Liberal Democrat MP said his new plans would address "hidden charges" from insurers to give retired workers a better deal.
It comes after an official advisory panel found retirees are often put off from shopping around because they face a bewildering variety of options in the UK's complex £12 billion annuities market.
Mr Webb said: "When you take out a mortgage, in a few years if rates change you can switch your mortgage.
"But when you take out an annuity, that's it - for life. This could easily be for a quarter of a century.
"Why shouldn't you be able to change your annuity provider so a few years later somebody else could offer you a bigger pension?"