Tony Blair today promised the Government would deliver on its manifesto promise to change the double jeopardy rule which prevents people being tried more than once for the same crime.

''For serious offences if there is overwhelming new evidence that implicates the accused again, they should go back to court,'' said the Prime Minister. ''It's perhaps the biggest miscarriage of justice in today's system when the guilty walk away unpunished.''

However the Prime Minister's promise still leaves open whether the new changes to the law will apply to past cases, including that of Billy Dunlop who confessed to the murder of pizza delivery girl Julie Hogg after being acquitted of the crime.

Julie's mother, Anne Ming, from Teesside condemned the decision earlier this year to delay the changes to the double jeopardy rules at the same time as allowing MPs to vote on banning fox hunting.

The Northern Echo is supporting Mrs Ming's campaign to abolish the double jeopardy rule and make it apply to past cases.

The Home Office yesterday refused to say whether the changes will apply retrospectively. ''You will have to wait for the White paper next month,'' said a spokesman.

However several MPs, including Stockton MPs Dari Taylor and Frank Cook, who have backed the campaign to change the law, are confident it will be retrospective.