A report on whether the rule breaches the Human Rights Convention is to be drawn up by the Council of Europe's Parliamentary Assembly, made up of national MPs from 47 countries.

The move, approved at the start of the Assembly's summer session at Council of Europe headquarters in Strasbourg, comes ahead of House of Lords consideration of the narrow Commons vote approving the controversial change.

The Assembly's Legal Affairs Committee is likely to appoint the report's author before the end of the week, with a debate on the findings expected in late September - adding to Prime Minister Gordon Brown's hurdles in getting the legislation through.

Michael Hancock, Liberal Democrat MP for Portsmouth South and one of the UK's 18 Westminster delegates on the Assembly, told the meeting that the Commons decision had been "a disgrace to our democratic system".

He told the Assembly: "This issue is very relevant to the whole principle the Council of Europe stands for. It goes against the grain of everything this Assembly stands for. In any other country it would be opposed immediately."

He said the issue was now going before the House of Lords and it would be "opportune" to have the Assembly express a view on the matter first.

Tory MP for Spelthorne David Wilshire said the UK Parliament had approved "giving police powers to knock on your door at six in the morning, take you to a police cell and lock you up for six weeks - 42 days - without telling you what you are accused of or giving you the evidence they have against you".

Mr Wilshire said he was ashamed of the decision which, he insisted, breached the Human Rights Convention: "We (the Assembly) must have an opinion on it."

Labour's Rotherham MP Denis MacShane said both men had inaccurately described "a very difficult decision of the House of Commons, now to be debated in the second House".