Foreign Secretary Jack Straw has moved to fend off claims that he is paving the way for a European super state by calling for a written EU constitution.

Mr Straw told business leaders in Scotland that a constitution could help tackle disillusionment with the EU among ordinary people.

This is a clear indication that they have now caved in to the Euro integrationalists

Michael Ancram Shadow foreign secretary

The speech has prompted the Conservatives to accuse ministers of trying to "sell out" British interests.

Mr Straw's comments came as he began a tour of the UK to showcase the benefits of European links and to promote his case for EU reform.

'Gridlock' fears

Mr Straw argued that devolution in the UK is a good example of how government can be brought closer to the people.

Later, he told BBC Radio 4's World At One programme that the EU's current systems were too complicated and were in danger of "breakdown".

A constitution would provide a "basic rulebook" for Europe's citizens, he said.

"At the moment the rules of the European Union are spread around a whole series of texts," he continued.

Michael Ancram says ministers are playing grandmother's footsteps

"They are pretty obscure and obtuse and much less accessible than they should be."

The foreign secretary also used his speech to call for a "subsidiarity" watchdog, made up of MPs from across the EU, who could vet unjustified European legislation.

The 1992 Maastricht Treaty had been "akin to passing criminal legislation whilst forgetting to establish a police force," he said.

In a gibe at Tory critics, Mr Straw said a constitution did not mean signing up to "every dot and comma of a European super state".

The Conservative Party itself had a constitution, he stressed.

What mattered was what the document contained.

'Covert integration'

A debate is under way over the future of a Europe which is expected to expand to 25 member states by 2004.

Mr Straw's announcement, which built on ideas he expressed to the BBC in February, comes at a time when some voters feel alienated by the EU.

Earlier, shadow foreign secretary Michael Ancram launched a strident criticism of the government's intentions.

Menzies Campbell says individuals' rights too must be defined

"This is a clear indication that they have now caved in to the Euro integrationalists, to the people who want to see full political union," he told BBC Radio 4's Today programme

"However, Jack Straw covers it up today, it is another step along what I regard as a sort of grandmother's footsteps game of moving towards European integration and hoping people aren't going to notice."

Mr Straw's speech won support from Liberal Democrat foreign affairs spokesman Menzies Campbell.

Mr Campbell warned that the rights of individuals, as well as member states, needed to be clearly defined.

But he said an EU constitution was needed to reverse "Europe's dislocation from ordinary Europeans".

Euro rally?

Labour MP Ian Davidson, chairman of Labour Against the Euro, said it was useful for Mr Straw to tell people about the UK's links with Europe.

But the foreign secretary was also trying to "drum up support for the euro", something he described as "like trying to breathe life into a corpse".

Labour peer Lord Haskins, a member of the pro-euro Britain in Europe group, hit back by claiming the currency had enjoyed a "calm and effective" start.

The pro-euro campaign would not get going until Gordon Brown had delivered his verdict on the five economic tests for entry, Lord Haskins told Today.

"Public opinion will change in a big way then," added the peer.