MPs are to launch an inquiry into the government's establishment of a "British Guantanamo" in Belmarsh prison.

The news came a day after the foreign secretary confirmed that the four Britons remaining in Guantanamo Bay are set to be released by the US authorities.

Jack Straw said that Moazzam Begg, Martin Mubanga, Richard Belmar and Feroz Abbasi will return to Britain "within the next few weeks".

On Wednesday the Commons constitutional affairs select committee confirmed that its latest inquiry would include a review of the UK government's continued detention without trial of foreign terrorist suspects.

Ministers say that unlike the Guantanamo detainees, those held by Britain are free to leave the country at any time.

But human rights campaigners have said that the government is guilty of the same human rights violations as the US administration - a view recently backed by law lords who ruled against the detentions.

The committee inquiry will focus on the Special Immigration Appeals Commission (SIAC), the court that sits in secret to hear appeals from terrorist suspects facing deportation or detention.

Committee chairman Alan Beith said that depriving a person of their liberty without charge or trial "is one of the gravest sanctions a state can impose".

"SIAC plays an integral role in this process and so it is vital that the government is able to demonstrate that this legal appeal process - the only one available to suspects - is sound," he added.

"Although SIAC is a court chaired by a judge, it meets in secret and the special advocates chosen to defend detainees' interests cannot tell them what the case against them is.

"We will be taking evidence from those who have been involved with SIAC as well as hearing from organisations and individuals with expert knowledge of this area."

The inquiry will examine the workings of SIAC, and consider how it impacts upon the legal and human rights of appellants.

MPs will also question whether it offers sufficient safeguards against inappropriate detention or deportation, and investigate whether procedures established to deal with immigration rights are adequate for decisions involving lengthy periods of custody.