Conservative and Liberal Democrat MPs are to try to block controversial plans to allow judges to sit without a jury in serious and complex fraud trials.
Judges alone could decide on 15-20 fraud cases a year
Ministers are asking the Commons to back the changes which would take effect from 1 January 2006.
The law was changed two years ago in the Criminal Justice Act 2003 but the proposals have not come into force.
Then Home Secretary David Blunkett said the plans would not be introduced until opposition parties had been consulted.
The judiciary, prosecuting authorities and others would also need to be asked about alternatives to non jury trials, he said at the time.
The government says that consultation took place at the start of this year when the Attorney General, Lord Goldsmith, held a seminar on the plans.
However, the Conservatives and Liberal Democrats are accusing the government of reneging on the undertaking given by Mr Blunkett two years ago.
A Commons motion has been tabled by Home Secretary Charles Clarke, asking MPs to approve the changes. A vote is likely to take place later this week.
Under the new procedure the prosecution will have to apply for a non jury trial.
A judge will have to decide whether it is in the interests of justice for a jury to hear the case.
'Not cutting costs'
The Lord Chief Justice will have the final say on whether the trial should go ahead without a jury.
The plan comes after a £60m fraud case collapsed after almost two years in court, partly due to jury problems.
The trial of six men, accused of bribing London Underground officials, was abandoned after being blighted by illness among jurors and legal delays.
The government has shunned the alternative of judges sitting alongside panels of experts or people with financial experience to decide cases.
Lord Goldsmith has insisted the measure was not aimed at cutting costs, but was in the interests of justice.
Some trials were currently too lengthy, too expensive and the jurors available for them were not representative of the population, he has said.
He is also worried that some fraud charges have to be dropped because they are too complicated.