The former NatWest executives deny any wrongdoing

Any appeal had been set to challenge the legal status of the UK's fast track extradition treaty with the US.

David Bermingham, Gary Mulgrew and Giles Darby have always maintained their innocence of "wire fraud" and say they should be tried by a UK jury.

In February the High Court said the case was "properly triable" in the US.

After that decision the High Court certified potential grounds of appeal to the House of Lords, but a committee of Law Lords refused a petition by the former NatWest bankers for permission to appeal.

Following the latest decision, their solicitor Mark Spragg said the Home Office had allowed seven days to apply to the European Court of Human Rights (ECHR) for a stay of the extradition order made in May 2005.

'Probable cause'

Enron collapsed in 2001 after admitting inflating profits and hiding debts.

Mr Bermingham of Goring, Oxfordshire, Mr Mulgrew, of Sible Hedingham, Essex, and Mr Darby, of Lower South Wraxall, Wiltshire, have been accused of seven counts of "wire fraud" by the US.

The three are alleged to have conspired with former Enron executives over the sale of part of the company in 2000, which made them a total of $7.3m (�4.2m).

Their case has generated criticism of extradition laws that mean the US is not required to provide "prima facie" or solid evidence of wrongdoing to extradite a UK citizen.

Britain must still provide the US with evidence of "probable cause" if it wishes to extradite someone from America.

The affair is being seen as a test case in the UK of the government's Extradition Act 2003 - which was developed in the wake of the 11 September attacks in 2001.