The Lib Dems have attacked the decision to build new nuclear power stations, saying the focus should be on renewable energy sources such as wind power.
Mr Webb said nuclear power was not the answer
Environment spokesman Steve Webb said he thought the plans were either a "white elephant or a red herring".
He told MPs alternative energy ideas were "evolving practically every day".
But Business Secretary John Hutton, who announced the government's proposals, said the Lib Dems still harboured "old prejudices" against nuclear power.
Mr Webb claimed the technology involved in the government's programme could be obsolete by the time any plants - the first of which is due around 2020 - were built.
He said: "Isn't there a danger with new nuclear that we are going to lock ourselves in rigidly to a technology, for the best part of a century, when other technologies like carbon capture and storage, like renewables, are evolving practically every day?"
Mr Webb added: "I can't decide whether new nuclear is a white elephant or a red herring.
"But very clearly what it isn't is the answer to the energy problems we face today."
Mr Hutton replied: "I'm all in favour of reducing emissions. I think we can start with what comes out of your mouth."
He added: "What's absolutely transparent from your contribution is that what we need and could benefit from in this House is some fresh thinking, not a rehash of all the old prejudices that have confused this debate for so long."
The Tories back the government's plans but insist the investment should be by businesses, with no subsidies from Whitehall.
Environmental groups say nuclear power is expensive and dangerous.