Home Office minister Paul Boateng accused Tory leader William Hague of pandering to popularism by supporting the abolition of the English law, which says no-one can be tried twice for the same crime.
"It is further evidence of Mr Hague's weak leadership that he has seen fit to discard the sensible and moderate approach for the sake of one day's headlines," he said.
Shadow home secretary Ann Widdecombe said scrapping the rule would allow serious crimes to be returned to the courts if substantial new evidence became available after an acquittal.
Mr Hague will outline the plans further in a speech to the Police Federation on Thursday.
Changes to the principle were first proposed by Sir William Macpherson in his report last year on the murder of black teenager Stephen Lawrence.
Home Secretary Jack Straw ordered the Law Commission of England and Wales to look into the issue, and an initial report last October backed Sir William's arguments.
Final, detailed proposals and a draft bill are expected next year.
Mr Boateng said the Conservatives were being irresponsible in pre-empting the commission's final report.
'Irresponsible'
"William Hague's knee-jerk headline seeking is yet another example of his poor judgement. The government accepted the Macpherson Report recommendation to consider this issue.
"The Law Commission is giving very careful consideration to this issue. That is the right way to deal with this important and sensitive matter.
"This way forward was accepted by wiser heads in the Tory Party when the Macpherson Report was published last year."
Leading civil rights group Liberty director, John Wadham, attacked the proposal as "macho" party politics.
"They are merely a macho contest between the Tories and Labour both of whom want to be seen to be the toughest on crime," he said.
"The protection from double jeopardy is a fundamental part of our criminal justice system and we remove it at our peril."
It is understood Mr Hague's concerns have been raised by the Stephen Lawrence case.
Three suspects in the Lawrence case were acquitted of murder in 1996 after the judge in a private prosecution brought by Stephen's parents found there was insufficient evidence for a guilty verdict.
Last month a knife was discovered buried in the garden of a house occupied by two of the suspects at the time of the murder in 1993.
But even if new evidence pointed to one of the three acquitted suspects they could not be charged with murder or any similar offence arising from the stabbing at a bus stop in south-east London in 1993.