The UK government will send a minister to the US to plead with the government to ratify an extradition treaty, amid a row over three former NatWest bankers.The “NatWest 3″ will be extradited to the US on Thursday over alleged fraud offences linked to bankrupt Enron.

Under the Extradition Act 2003 the men can be extradited to the US under a fast-track process, and tried there.

But the treaty has not been ratified in the US, which means the UK does not have a reciprocal legal arrangement.

‘Probable cause’

Baroness Scotland will fly to the US on Thursday - the day the men are to be extradited - in a hope of addressing the issue.

UK politicians and business leaders have criticised the current arrangements because the US has been slow to ratify the treaty.

The treaty was originally intended to tackle terrorist suspects.

It means UK courts do not require the US to provide “prima facie” or solid evidence of wrongdoing to extradite a UK citizen.

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

Former NatWest employees 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.

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

There have been growing misgivings about their situation, with opposition politicians and business leaders criticising the attorney general’s decision to refuse a UK trial.

‘Frustration’

Now the Home Secretary John Reid has ordered that the Home Office’s Baroness Scotland fly to the US to request reciprocity.

She is not asking for the case to be tried in the UK but for the US to ratify the treaty from its end. The Treaty needs a two-thirds majority in the US Senate to pass.

The flight to the US comes as opposition leaders want the House of Lords to amend the Extradition Act to end the arrangement.

In Monday’s Financial Times, Baroness Scotland wrote: “I want to have the opportunity to explain face to face our frustration at the Senate’s delay [in signing] without having to defend a spurious and wrong-headed amendment designed to score an anti-American party political point.”

Attorney General Lord Goldsmith has been firm in saying there is “no basis” to examine again the Serious Fraud Office’s decision to let the US deal with the case and not prosecute in the UK.