British ministers believe US interrogators could be guilty of torturing and abusing Moazzam Begg, one of the Britons released from Guantanamo Bay last month, The Independent on Sunday has learned.

British ministers believe US interrogators could be guilty of torturing and abusing Moazzam Begg, one of the Britons released from Guantanamo Bay last month, The Independent on Sunday has learned.

Britain has rejected initial claims by the Pentagon that Mr Begg's allegations are unfounded, and has insisted that the US launches a second, more intensive, inquiry into his case.

The Foreign Office believes that Mr Begg, a former bookseller from Birmingham, has made "credible" allegations that he was severely ill treated by US intelligence officers at Bagram air base in Afghanistan three years ago. A source said: "There is genuine concern about the allegations which have been made. We want a proper investigation."

It has also emerged that ministers have complained in private to the US and Iraqi authorities about alleged abuses of Iraqi civilians and prisoners, after highly critical Red Cross reports and the scandal over sexual assaults at Abu Ghraib prison came to light.

Mr Begg, 35, was released from Guantanamo last month with three other Britons, ending a three-year ordeal that included 18 months of solitary confinement. He claims he was interrogated 250 times during his detention.

The former detainee, who was reunited with his father, wife and three children three weeks ago, is understood to be undergoing psychiatric treatment and medical checks after suffering mental health problems and severe weight loss.

The US designated Mr Begg an "enemy combatant" and accused him of being an al-Qa'ida activist. He had moved to the Afghan capital, Kabul, in July 2001 to open an Islamic school, allegedly attended by the children of senior al-Qa'ida and Taliban officials.

A money order in his name was allegedly found in an al-Qa'ida building after the US ousted the Taliban. The US also accused him of fighting in al-Qa'ida's last stand in the Tora Bora mountains - a charge he denies.

Mr Begg, who was arrested in the Pakistani capital, Islamabad, on 31 January 2002, alleges that US officials in Afghanistan subjected him to repeated and prolonged periods of torture and abusive interrogations, which included threats against his life.

In a lengthy statement he wrote in Guantanamo Bay last year, Mr Begg claims that during his year-long detention at Bagram he was stripped, denied light and fresh food, and that he witnessed the alleged murder of two other detainees.

He alleges his interrogators then confronted him at Guantanamo and coerced him into signing a false confession.

British officials believe Mr Begg's claims were substantiated by official US military inquiries, which found last year that detainees were abused at Bagram. US intelligence officers are facing trial over the deaths of two detainees in Afghanistan. The inquiries said illegal and abusive interrogation tactics developed in Afghanistan were used in Guantanamo and in Iraq.

British lawyers and human rights groups will be sceptical about the Government's stance on rights abuses. Ministers have insisted in court hearings they should be allowed to use material from Guantanamo detainees in British terror cases, even if those confessions were extracted under torture.

The British intelligence services are also accused of helping the US to illegally arrest Britons such as Martin Mubanga in Zambia and the British resident Bisher al-Rawi in Ghana, and move them to Guantanamo.

Mr Begg's lawyer, Gareth Peirce, said yesterday that the Government's demands for a US inquiry were "too little, too late. It is impossible to wind the clock back. They were complicit in an unlawful capture from the beginning. In the years to come, Moazzam's account of what happened to him will be seen as the template for accuracy and truth."