Former Labour leader Neil Kinnock has branded Tony Blair's school reforms "educational crazy paving".
Lord Kinnock says the reforms are an inconsistent "mosaic"
Lord Kinnock said the government's plans to create "trust" schools with more independence would perpetuate social and education differences.
The plans contained a "tragic inconsistency" and were little different to the grant-maintained schools seen under the Tories, he said.
Lord Kinnock was speaking as the House of Lords began debating the proposals.
Tony Blair has already won MPs backing for the reforms, but only by relying on Conservative support in the face of a revolt from Labour backbenchers.
The government has reassured some Labour rebels who originally spoke out against the trust school plans, but Lord Kinnock is not among them.
He told peers: "The tragic inconsistency is that parts of this bill, which reinforce further progress towards excellence and equity for every child, are contradicted by the provisions that seek to put all of England's primary and secondary schools into the ownership and governance of independent foundation trusts."
Lord Kinnock accused ministers of being fixated on structures rather than focusing on school standards.
The government thought education achievement could be boosted across the board by having more types of schools and operating a market governed mainly by interests outside schools and local communities, he said.
"Each component of that doctrine is mistaken," he said.
Lord Kinnock said a market system had relative winners and relative losers. In schooling, losing too often was for life and so could not be afforded.
Lib Dem education spokesman Baroness Walmsley told peers: "This is a cruel confidence trick - the government are, in one blow, removing democratic accountability, making it difficult for parents to exercise real choice and setting school against school."
Ministers insist that encouraging innovation in schools can raise standards and avoid inequalities.
Concluding the debate, Education Minister Lord Adonis said there was broad agreement on the plans.
"We all agree that increased investment in education is crucial," he told peers.
"We also all agree that it is right to focus on disadvantage. No-one has called for a return to a national system of selection at age 11 and that is a seminal moment in the debate on education.
"We agree that we want collaboration and competition. What parents value most of all is good local schools and everyone has accepted that we need far more improvements. I see trust schools as a sensible, pragmatic reform."
Along with convention, peers gave the Education and Inspections Bill a second reading without a vote.