Shadow housing minister Grant Shapps claimed the project would only deliver a tiny fraction of the homes needed to meet the national shortage and the dwellings would be built to lower environmental standards than other developments.
He said more properties would be built working with local communities rather than through a "Soviet-style" Whitehall project.
The Government is considering 15 proposals for the new towns, which will aim to tackle both the housing shortage and the problem of climate change.
But Mr Shapps said: "The problem is that there's almost nothing green left about these plans whatsoever."
The scheme had "descended into the sort of farce" seen with the introduction of the Home Information packs, he claimed.
He claimed the proposed new towns would only provide around 75,000 homes by 2016 and would only be built at the Government's Sustainability Code 3 - when all other properties built in 2016 would be at Code 6.
He told MPs: "The simple fact is more homes can be produced when you work with communities rather than coming up with large, centrally-driven, Whitehall-driven, top-down, Soviet-style planning from the centre."
Opening the Commons topical debate housing minister Caroline Flint said the "exciting" proposals would create sustainable communities rather than simply green homes.
She said: "Eco-towns offer us a unique opportunity not only to address the housing shortage and to tackle climate change, but also to seek to trigger economic growth across a whole area."
Ms Flint said: "The eco-town programme allows us to see if there are ways within a whole town development to demonstrate how in this country ... we can become world leaders in what will be, increasingly, the way in which we will build houses in the future."
Mr Shapps said there was "very little chance" of the projects proceeding through to being built and said it was "logistically impossible" to build the scale of homes laid down by the Government.
He said the plan was "falling apart" and ministers should scrap it.
But Labour former housing minister Nick Raynsford said there was a very strong case for new towns and urged the Tories to be more constructive.