Sally-Anne Croft, 42, and Susan Hagan, 45, face charges of being members of a conspiracy to murder Charles Turner, a US federal attorney, in Oregon eight years ago when they were followers of Bhagwan Shree Rajneesh. The commune the Indian guru and multi-millionaire founded in Oregon collapsed amid bitter internal strife and confrontations with the US authorities in 1985.
The intervention by leading Opposition politicians promises to turn the cases into an embarrassing political issue for the Home Office. Lawyers for the women allege that the Government would rather 'quietly sacrifice' the two rather than offend the US authorities and hamper efforts to get IRA suspects extradited.
The lawyers have sent Kenneth Clarke, the Home Secretary, a huge body of legal opinions from the former law lord Lord Scarman, High Court judges, MPs and extradition lawyers, all stating that the women are the victims of a miscarriage of justice.
Ms Croft, a senior accountant with Ernst & Young, and Ms Hagan, a mother of two and an aromatherapist, face sentences of 20 years to life in an Oregon jail if they do not enter into plea- bargaining deals with the US authorities.
As the Independent on Sunday revealed in December, no attempt was made on Mr Turner's life, and the evidence that the two women were ever part of a fruitlessconspiracy to kill him was not produced for five years.
When it came, it was based solely on the confessions of former commune members who had made 'sweetheart deals' with the authorities. The witnesses will face huge increases in their sentences if they change their stories in court.
The Americans have refused to move the trial from Oregon - where local anger against Rajneesh followers is still very strong - and have further declined to allow the defence to see witnesses' statements.
In a letter to Mr Clarke, Mr Blair said the evidence against Ms Croft and Ms Hagan was 'insubstantial and uncorroborated'. He warned of the dangers of a prejudiced trial in Oregon and said there was 'a real risk of a miscarriage of justice'. Mr Ashdown told the Home Secretary: 'I am horrified that this couple could be facing extradition. There is no case for acceding to a request for extradition.'
Lord Longford, the campaigner for prisoners' rights, has asked that the US Justice Department intervene. He said the Oregon authorities were pursuing a vendetta against Ms Croft and Ms Hagan and the case should be dropped.
Partners in Ernst & Young have written to Mr Clarke asking him to intervene and stop the extradition. The charge against Ms Croft 'has not diminished our confidence in her', they said. 'We believe Ms Croft is innocent of the accusations.'
Lord Scarman has already told Mr Clarke that it would be a miscarriage of justice to send the women back.
He said the delays in bringing the case were 'intolerable and oppressive' and the refusal of the Americans to allow the women to see witnesses' statements 'was an oppressive restriction on the rights of the defence'.
Andrew McCooey, the women's solicitor, said yesterday: 'I strongly urge Kenneth Clarke not to sacrifice the lives of two innocent British women for the sake of Anglo-US relations.'
The Home Office said that a decision would be announced shortly.