Birmingham MP Lynne Jones is to lead a Labour rebellion against the Government's plans for identity cards.
The Labour MP for Selly Oak will propose an amendment to scrap the proposals, when the Identity Cards Bill receives its second reading in the Commons tonight.
Labour backbenchers backing the amendment include fellow Birmingham MP Clare Short (Lab Ladywood). The Prime Minister defended ID cards yesterday, calling them "an idea whose time has come".
Mr Blair insisted the rebellion would fail. He said: "I am confident we can get the Bill on the statute book and I am also confident that in principle we have public support."
But in a fresh setback for the proposals, academics warned the scheme could cost £19.2 billion.
A team of researchers from the London School of Economics warned the cost of an ID card would be between £170 and £230 per person - far more than the Government's estimate of between £90 and £110.
However, Ministers also received a boost when a poll found 61 per cent of voters supported ID cards.
The survey found 53 per cent of people in the West Midlands backed the scheme.
Identity cards will be issued from 2008, if they receive the backing of MPs.
They will includen clud e microchips with biometric information such as a person's fingerprints or iris or facial scans, as well as a photograph and the name, address, gender and date of birth of the holder.
Dr Jones said: "I know many colleagues feel that this was a manifesto commitment and therefore they are bound to support it.
"But the particular scheme the Government is proposing is fundamentally flawed and won't achieve what we want it to achieve." Ms Short said the Government had failed to make the case for ID cards and accused Mr Blair of using the issue in an attempt to prove himself a "macho" leader.
"He is an absolute control freak. He wants to control everything from No 10. It's 'War on terror, this is modern, let's have lots of control and authority'. It sounds strong, he wants to be a macho leader. That's the way he is.
"I don't think the case has been made for this fantastic intrusion into our lives."
Mr Blair said biometric passports, which are similar to identity cards, would soon be needed anyway.
The United States was planning to turn away visitors without them, while the EU had already agreed member states should begin to include biometrics in their passports from 2006, he said.
Mr Blair said: "We are going to be in a position where we have to make our passports here in the UK biometric if UK citizens are to continue to enjoy the right to travel freely around the world."
It would only cost about £30 per person to turn biometric passports into identity cards, which had a number of advantages, he said.
"People recognise the benefits of a scheme that will allow us to tackle identity fraud more effectively, bear down on illegal working, illegal immigration, abuse of our public services and help in the fight against organised crime and terrorism."