Nuclear weapons treaty may be illegal

The two countries recently negotiated an amendment to a mutual defence agreement first made in 1958 and regarded in Whitehall as a cornerstone of the special relationship.

The government made no reference to the negotiations until after they were completed and it has now ratified the amended treaty without a debate in parliament.

Last month George Bush said the treaty helped Britain maintain a "credible nuclear force".

But two senior lawyers have said there is a strong case that the US-UK mutual defence agreement breaches the nuclear non-proliferation treaty.

Rabinder Singh QC and Christine Chinkin argue that the non-proliferation treaty forbids the transfer of nuclear weapons or devices. Renewal of the defence agreement is intended to "continue and enhance Britain's nuclear programme". The lawyers claim the non-proliferation treaty takes precedence over the agreement under international law.

The Commons defence committee has declined to inquire into the amended defence agreement with the US.