First there was Camp X-Ray on the American-owned base of Guantanamo Bay in Cuba. Now there is a Camp Justice in the Indian Ocean on the British-owned island of Diego Garcia, which is leased to the Americans.

Camp Justice is officially a temporary home for US personnel supporting Operation Enduring Freedom, but satellite pictures of the camp show something rather more permanent and on a large scale. The island is home to American B52 and Stealth bombers - and has been home to US support staff and other military services since the early 1970s - but Camp Justice is new. The question is: what is the camp's real purpose and how far does British jurisdiction stretch?

The Liberal Democrats' Foreign Affairs spokesman, Menzies Campbell, might be interested to look at these same satellite pictures of Camp Justice. (They can be found on the website of a US-based security and risk assessment company, Global Security, on www.global security.org.) Last week Mr Campbell demanded to know whether information from "rendered" - in other words, tortured - al-Qa'ida and other suspects could be acceptable as evidence in a British court.

He did so in the knowledge that serious claims have been made in The Washington Post that some suspects have been sent for "rendering" in Yemen, Jordan and Syria, where unjustifiable interrogation techniques are often used.

More significantly for our own government, The Washington Post has claimed that prisoners are now being held on the island of Diego Garcia for "rendering", before being transferred to Camp X-Ray. These reports were strenuously denied by the then Foreign Office Minister, Baroness Amos. Replying to the former Labour MEP and veteran peace and justice campaigner, Professor Ken Coates, Baroness Amos had this to say: "The United States government would need to ask for our permission to bring any suspects to Diego Garcia. It has not done so."

However, Time magazine has recently claimed that Riduan Isamuddin, otherwise known as Hambali, who is believed to be operations chief of Jemaah Isalmiyah - the group behind the Bali bombing - has or is still being held on Diego Garcia. Meanwhile, Mauritius-based campaigners Lindsey Collen and Ragini Kistnasamy, who seek the closure of the US military base on the island, had this message for campaigners in Britain: "Now there is the whole Guantano-isation of Diego Garcia, with people on terrorism charges and members of the Iraqi leadership being held there."

When it comes to obfuscation over Diego Garcia, successive British governments have become past masters at doublespeak. It was a Labour defence minister, Lord Chalfont, who bundled the original inhabitants of the island to the slums of Port Louis in Mauritius, 30 years ago to make way for one of America's largest military bases. Ever since ministers have sought to avoid embarrassment over a sordid episode they - and the courts - would rather forget.

Barton Gelman, The Washington Post gumshoe, has this to say of Baroness Amos's original denial: "Our experience with spokesmen most likely mirrors yours. They persuade themselves sometimes that they avoid a lie (while appearing to call something true, false) by using private definitions of ordinary language. What we have from our sources is that some al-Qa'ida suspects are indeed being held and questioned at Diego Garcia. The British Government could go some way to clearing this up by permitting an unrestricted visit."

Chance would be a fine thing, if the experience of the original inhabitants were anything to go by. The islanders won their High Court battle to be allowed to return home three years ago. A fortnight ago I came across a group of them huddled in the rain in Parliament Square under their national flag - a Union flag on a shield supported by two turtles. They told me that they were still being prevented from returning because the US didn't want them and the British say that the cost of restoring a basic infrastructure is too much.

The island of Diego Garcia, some 17 square miles, is a permanent floating aircraft carrier, where despite government denials, terrorist suspects may be being "rendered" at a place called Camp Justice, a camp where no journalist has been permitted entrance. There could be no objections if terrorist suspects were brought to Diego Garcia and immediately handed over to the judge and magistrate who, along with the "BritRep" and 50 or so Marines, have responsibility for what is known as the British Indian Ocean Territory, and of which Diego Garcia is part. There they could be charged under British law on what remains British territory.

But The Washington Post, Time magazine and all of us who have been campaigning over Diego Garcia for as long as we can remember doubt that is what is happening and simply do not believe what we have been told by Baroness Amos. And if it is the case that prisoners are being held on Diego Garcia in contravention of British law, it might go some way to explaining the lacklustre attempts by Tony Blair to persuade George Bush to budge on British-born prisoners held at Guantanamo Bay.

Campaigners Menzies Campbell, Helena Kennedy, Tam Dalyell, Ken Coates - all of them could demand open and unrestricted access to Camp Justice on Diego Garcia. It is now the only way of establishing the truth.