A British inquiry into alleged complicity in the mistreatment of terror suspects will look into new claims that the spy agency MI6 was involved in rendition to Libya, a spokesman said yesterday.

Prime Minister David Cameron set up the Gibson inquiry in July 2010 to probe allegations that British intelligence were complicit in the torture of extremists on foreign soil after the September 11, 2001 attacks on the US.

The inquiry had focused on Guantanamo Bay detainees but decided to examine British links to the ousted Libyan regime after the discovery at the weekend of files in Tripoli which suggested MI6 involvement in rendition to Libya.Abdelhakim Belhaj, now the Libyan rebels’ military commander in Tripoli, has demanded an apology after the files suggested Britain and the US were complicit in a plan that led to his illegal transfer to Libya and subsequent torture.

Mr Belhaj was named as a senior member of the Libyan Islamic Fighting Group (LIFG), which fought to overthrow Colonel Gaddafi. It had historical ties to Al-Qaeda.

Files unearthed from Col Gaddafi’s intelligence archives documented the capture by the CIA of Abdelhakim Belhaj in Bangkok in 2004 and his forcible repatriation to Libya, where he had fought the old regime. He was then jailed in Tripoli’s notorious Abu Slim prison for seven years and maintains he was questioned there by British intelligence officers. Mr Belhaj, now military commander of Tripoli, told the BBC: “What happened to me was illegal and deserves an apology.”

Britain’s Guardian newspaper yesterday quoted him as saying he was considering suing both governments. “I was injected with something, hung from a wall by my arms and legs and put in a container surrounded by ice,” he said of his time in prison. “They did not let me sleep and there was noise all the time. I was regularly tortured. I’m surprised that the British got involved in what was a very painful period in my life,” he added.