Chris Patten

As an intervention from Chris Patten stokes up the euro debate, a new poll has found that a clear majority of the public remains opposed to British membership of the single currency.

Amid reports that Tony Blair is set to give senior Cabinet ministers free reign to promote the benefits of joining the single currency, the latest figures suggest they face a tough task in winning over the voters.

The poll came as the European Union's external relations commissioner mounted an outspoken attack on the prime minister for failing to stand up to Gordon Brown over the euro.

Patten told BBC Radio 4's Today programme that it was "drivel" to claim the Treasury's five tests on euro entry were "absolute economic truth".

He said there were key arguments to be made on issues such as economic reform, the future of the EU and relations with America.

"Mr Blair's strength in putting those arguments will to a degree be hollowed out if Britain is felt to be semi-detached from the overall European enterprise and if Mr Blair is thought to be rolled over by Mr Brown," he said.

Meanwhile, Lord Simon, the former trade minister and adviser to the prime minister has called for a "road map" to joining the single currency.

The interventions came as a YouGov poll for Sky News found a majority of two to one against joining the euro.

Opposition to joining the euro is now greater than it was in June 2002, when 51 per cent were against joining and 41 per cent were in favour.

But pro-euro campaigners will take some comfort from figures suggesting that while they may be sceptical, a large section of the British public regards it as inevitable that the UK will join eventually.

Three quarters of those surveyed think that Britain will be a member of the euro within the next ten years, while over half expect to scrap the pound within five years.

With Gordon Brown placing the emphasis on the economic credibility of his five tests, there were also indications that criticisms of the eurozone's "one size fits all" interest rate policy were having an effect.

Of those questioned, half think that joining the euro will weaken Britain's economy while just 22 per cent think membership of the euro will strengthen it.

YouGov questioned a representative sample of 2465 electors online between May 9 and 12, a period which included a weekend of euro-dominated news headlines as reports of government splits on the issue surfaced.

Matthew Taylor, the Liberal Democrat's Treasury spokesman, said the latest twist in the euro saga showed the five tests were a matter of judgement rather than fact.

"With investment in Britain collapsing faster than in any of our European competitors, clearly the prime minister believes it is in Britain's interests to join, while the chancellor is afraid a botched referendum would destroy his chances of getting the top job," he said.