Mr Clarke defended his role with a tobacco company

And he repeated his call for the Conservatives to end their "obsession" with Europe and concentrate on fighting Tony Blair on the core issue of public services.

Mr Clarke ridiculed critics who accused him of "flogging fags to the Third World" during a business trip to Vietnam last week.

Mr Clarke dismissed allegations from the lobby group Action on Smoking and Health that he was "soiled" by his �100,000 a year directorship with British American Tobacco.

I am not setting out to play a game of football

Ken Clarke on why age is no barrier

He denounced the group and told the BBC: "I have been a smoker all my life and I respect the right of others to smoke, provided they don't annoy or inconvenience others," he told the BBC.

He said he would be happy to forego the money he earned from his directorships in return for being leader of the opposition.

Mr Clarke again poured scorn on the present party leadership and its concentration on Europe in the general election.

Disaster

"The Save the Pound election was as big a disaster for the Conservatives as the Ban the Bomb election was for Labour in 1983," he said.

Ken Clarke's directorships

BAT: �100,000 a year Alliance Unichem: �125,000 Foreign and Colonial Investment Trust: �23,000

The Conservatives should ditch the "extreme language" and "extreme policies" on Europe such as opposition to the Nice Treaty, he said.

He denied he would fail to find support for his pro-euro views from the shadow cabinet, fellow MPs, party members or the general public.

Age 'no barrier'

But, he added, being a "hardline eurosceptic" was the "only qualification" in many cases for being in William Hague's shadow cabinet.

Mr Clarke also insisted age - he will be 61 on Monday - was no barrier to high office.

"I am not setting out to play a game of football," he told Sky News.

As well as his directorships, Mr Clarke earns a living from speaking engagements and occasional journalism.

He also receives a �50,000 salary as MP for Rushcliffe in Nottinghamshire.

Popular brands

BAT claims to sell one in six of the cigarettes bought by the one billion people who "choose to smoke".

In Vietnam, its popular brands include State Express 55 and Lucky Strike.

A message from Mr Clarke on the BAT website describes the firm as "one of the most advanced and responsible British companies I have come across."