Tony Blair could lose his job if he fails to secure a yes vote in a referendum on the euro, according to a former Labour foreign secretary.

Lord Owen said the prime minister would be "destroyed" if he called a referendum and lost.

You cannot go to the country on a major issue as prime minister and be defeated and then expect to carry on in the same way

Lord Owen

Lord Owen's comments came a day after former Conservative deputy prime minister Lord Heseltine urged Mr Blair to take a strong lead in favour of the single currency.

But Tory foreign affairs spokesman Michael Ancram said his party would continue to campaign to keep the pound.

Lord Owen - who opposes UK membership of the euro - said Mr Blair risked losing his "personal authority" if people rejected the single currency.

"You cannot go to the country on a major issue as prime minister and be defeated and then expect to carry on in the same way - that is the risk of a referendum," he told GMTV's Sunday programme.

But the chairman of the influential Commons Treasury select committee, Labour's John McFall, told the BBC's On the Record that there should be a referendum on the issue next year.

Colleague Jane Griffiths told the same programme that there was a "groundswell" of opinion among Labour MPs that Chancellor Gordon Brown's five economic tests had already been met.

Softening?

Lord Owen, who left Labour to co-found the now defunct SDP, predicted Mr Brown would take over from Mr Blair if the prime minister stepped down.

Lord Heseltine said on Saturday that opposition to the euro was softening.

He welcomed the prime minister's recent positive comments on the subject and declared he could stake a place in history if he led Britain into joining.

Lord Heseltine's comments came as a new poll suggested more people trust Mr Brown's judgement on Europe than Mr Blair.

He said: "It seems to me that the only ingredient missing in the recipe for British membership of the euro is political leadership - and has been for some time.

Lord Heseltine said a successful referendum depended on the prime minister's leadership and without it "the pro-European supporters will remain reluctant and hesitant."

He said: "The best evidence for the success of the euro will be the experience of the 25 million Brits who will travel to the continent this year.

"What they will see and hear in the real world of the euro-zone will be far more eloquent than the strident over-exaggerated language of the euro-sceptic pressure groups."

'Entry is essential'

The boss of the GMB union, John Edmonds, said that UK entry into the euro was essential if the decline in manufacturing was to be reversed.

The problems caused by the high pound would be removed if people backed joining the euro.

He predicted the government could win a referendum if it was held next year.

Will British holidaymakers support the new currency?

"Most of the people's opinions in this country are pretty soft and they are looking for leadership from the government," he told GMTV.

But Mr Edmonds said "the only choice" was have a referendum next year.

A Sunday Times survey suggests 36% of people trust Mr Brown to make the right decision over euro entry compared to 13% who trust Mr Blair.

The online survey by YouGov conducted on Thursday and Friday suggested 51% of people expected a referendum in the next 12 months, while 31% did not.