Tony Blair says his school reforms mark an "important moment for the government", as he tries to win over Labour rebels opposed to the plans.
He said proposals in the Education Bill, due to be published on Tuesday, were "absolutely the crux of what a Labour government is about".
He will address concerns over the plans during a regular meeting of the parliamentary Labour party on Monday.
Speaking at Number 10, he said state education was not yet good enough.
'Change needed'
He said it was time to build on the "massive" investments ministers have put into public services and push up standards throughout the system.
He made the remarks as the government attempts to win the backing of up to 100 Labour rebels for its controversial plans to give schools greater freedom.
Mr Blair said: "Whilst there still remain significant numbers of young people not getting the education they need, even though things are far better than they were a decade ago, we have got to continue with change.
"Change in order to help children - particularly those from the most disadvantaged backgrounds, but not only those children - to do better and fulfil their potential.
"For me this is absolutely the crux of what a Labour Government is about.
"We have put in the investment, but people need to see those results there. We can point to great progress so far, but it isn't good enough yet."
'Confident Kelly'
Up to 100 Labour MPs have been critical of the plans, which are now expected to include a ban on selection by academic ability, including the use of interviews of children or parents.
Education Secretary Ruth Kelly said she would retain the right to veto councils' attempts to set up comprehensives under the new legislation.
However, relinquishing the veto is one of the key demands of the rebels who are threatening to vote against the prime minister over the bill.
Despite her refusal to back down, Ms Kelly said she believed most Labour MPs would accept the proposals would be good for children and give them their backing.
That strategy was tempered by a Ј30m "carrot" for local authorities to spend on failing schools.
'No selection'
Labour critics have feared the new bill could set up a two-tier education system by allowing schools to pick the best students to help improve their exam pass rates.
Under the plans, private companies, faith groups and parents, will be given freedom to set up and run schools under the state system.
It will also allow existing schools the freedom to develop "partnerships" with outside organisations and establish "federations" with neighbouring secondary schools.
But Ms Kelly said: "There was a fear that schools would use some of their new freedoms in order to manipulate their intake. I have always been completely adamant that that is something that we, that I, that the government would not tolerate.
"We have been completely clear that there can be no new selection by academic ability. In order to make that clear to everybody, so everybody knows there is a clear and transparent and robust system, we are going to write that on the face of the bill."
Tory support
Ms Kelly joined Mr Blair at a Downing Street seminar on Monday to talk to local authority leaders and address concerns about the strategic role of local education authorities and their thoughts on new trust schools.
Former Education Secretary David Blunkett told BBC Radio Five Live that asking for Tory MPs' support to pass the bill would be "unfortunate and undesirable".
Shadow education secretary David Willetts said his party would try to restore some of the bill's "original radicalism" as it went through the Commons.
He said he regretted the concessions to date, but pledged that it was even "a step in the right direction", the Tories would support it.
Ed Davey, the Liberal Democrats education spokesman, described the Ј30m promise as a "desperate" measure to appease rebels.
(BBC)
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