Tony Blair and Conservative leader David Cameron have accused each other of "flip-flopping" over policy.
During prime minister's questions on Wednesday, Mr Cameron said Mr Blair was "going backwards" on education reforms to "appease" Labour backbenchers.
But Mr Blair said his opposite number had reversed Tory policy on health, asylum quotas, Section 28, licensing and anti-social behaviour legislation.
He said as a result Mr Cameron was losing "any credibility".
'Thought we agreed?'
Some 91 Labour MPs have called for safeguards to prevent "back-door" selection if "trust" schools - with more say over admissions and budgets - are introduced.
Conservatives are supporting the plans, outlined in the government's Education White Paper.
Mr Blair said compromises offered on Monday to head off a potential rebellion by Labour backbenchers would not prevent greater independence for state schools.
Mr Cameron said: "Isn't it time you faced down the rebels and did the right thing for teachers, for parents and for pupils."
He added: "Why are you trying to appease those who don't want reform when you could be working with those who want it?"
But Mr Blair told Mr Cameron: "The fact of the matter is we will have those freedoms for schools, but yes we will ensure that they cannot go back to academic selection.
"That's a position I thought we both agreed upon."
Meanwhile, most backbench Labour opponents of school reforms remain unconvinced by compromises offered by ministers, a BBC poll suggests.
Sixty-two of the 91 MPs who have signed up to an "alternative" version of the white paper were questioned by Newsnight.
Of these, 45 said they had yet to be convinced by the government, while eight said they were satisfied.
Six backbenchers were undecided and three did not respond to the survey.
The Education Bill resulting from the white paper is due to be published later this month.