Emergency government talks were taking place behind the scenes last night on pursuing urgent legislation allowing witnesses to give anonymous evidence in the most serious court cases.

Emergency government talks were taking place behind the scenes last night on pursuing urgent legislation allowing witnesses to give anonymous evidence in the most serious court cases.

The move came after yesterday's collapse of a £6m murder trial following last week's Law Lords ruling that witnesses should not be allowed to give evidence anonymously.

The Old Bailey trial of two men accused of the shooting of the east London businessman Charles Butler - which had heard two months of evidence - became the first casualty of the ruling.

Evidence given by an anonymous witness was a key part of the prosecution case, and it has been estimated that a further 40 cases south of the Border could be affected by the ruling. Dozens more trials were said to be effectively put on hold as prosecutors assess the wide-ranging implications of the ruling.

Legal experts believe a small number of cases in Scotland could also be affected.

Police and prosecutors want the use of anonymous witnesses to be enshrined in law before parliament rises for the summer recess.

Observers say that if a solution cannot be found in the next 28 days, courts could face a deluge of appeals at a potentially huge cost to the taxpayer.

The Justice Secretary, Jack Straw, was expected to meet his Tory counterpart, Dominic Grieve, and the Shadow Minister for Police Reform, Nick Herbert, in the Commons yesterday.

There was also growing pressure on the Scottish Government to clarify the position for Scottish courts in the wake of the ruling.

Last night, the Scottish Government and the Crown Office said it would examine whether there were any implications for Scots law and were not speculating on its effect.

Leading QC Paul McBride said evidence given with complete anonymity was not normal practice in Scotland.

But he added that the Law Lords ruling was "quite frankly, utterly preposterous. There should, in due course, be legislation in England and possibly in Scotland to ensure this situation never happens again.

"There could be rare cases in Scotland for operational and security reasons where accused people should not be able to see certain people giving evidence against them," he said.

David Sinclair, head of communications with Victim Support Scotland, said the legal position north of the Border needed clarifying.

"There have been instances in the past where the anonymity of witnesses has been an important part of prosecutions, and, following the Law Lords ruling, Victim Support Scotland hopes that the matter will be studied carefully by the Crown Office and the government and that the position of witnesses in trials will be clarified.

"It is in the direct interest of witnesses and people likely to give evidence in major criminal trials that it be done as speedily as possible in the interests of trials and prosecutions in Scotland and to ensure that victims and witnesses giving evidence in trials have maximum possible protection under the law."

Bill McVicar, convener of the Law Society of Scotland's Criminal Law Committee, said the Law Lords ruling was "persuasive" to the legal system north of the Border but it would be difficult to clarify the position in Scottish courts without a test case.

The implications of the Law Lords ruling became clear at the Old Bailey yesterday when the £6m trial of two men accused of murder collapsed. Douglas Johnson, 27, and David Austin, 41, will be retried over the contract killing of London businessman Charles Butler, 50, next year.

Lawyers for two of the four men found guilty of murdering Birmingham teenagers Charlene Ellis and Letisha Shakespeare said they plan to appeal following the ruling.