He delivered a statement after the 'Stockade' prosecution ended in failure when the Court of Appeal quashed convictions against seven people accused in connection with the alleged diversion of £105m in excise duty and the likely successful appeals by 90 others convicted in a related series of prosecutions.

Healey said the Butterfield Review of the conduct of excise diversion cases which resulted in the loss of up to £2bn in revenue - several times higher than earlier estimates which ran into the hundreds of millions - will take the Operation Stockade debacle into account.

He said Mr Justice Butterfield will report by June on what went wrong and what is needed to prevent a repetition and pledged he will have 'unrestricted access to Customs staff, facilities and papers'.

He claimed changes have already been made in the way Customs investigations and prosecutions are handled following the similar collapse of the London City Bond cases, including the appointment of a new Customs chairman and transfer of responsibility for prosecutions to the Lord Advocate.

The attack came from Tory spokesman Stephen O'Brien who alleged 'mess and confusion' which had cost £100m in legal fees on top of revenue losses.

And Liberal Democrat spokesman Matthew Taylor demanded to know whether ministers had personally authorised lawbreaking to trap suspects.

Healey denied any 'entrapment' and said the use of informants to allow fraud to run was an established practice.

He said the prosecutions were necessarily long and complex and involved issues over the use of informants, documentation and disclosure dating from the mid-1990s and the government were already acting to reduce the risk of recurrence.