By Andrew Benson

Ecclestone said he was prepared to sign a letter asking for Mosley to resign

The pressure on embattled motorsport boss Max Mosley has increased after it emerged Formula One supremo Bernie Ecclestone wants him to resign.

Ecclestone invited F1 team principals to sign a letter calling for Mosley to stand down and said he would add his name if they all signed it.

Seven teams agreed, but three did not - Ferrari, Toro Rosso and Williams.

Mosley was accused by a newspaper of taking part in a "Nazi-style orgy". He denies his deeds had Nazi connotations.

The Super Aguri team, whose future is in doubt because of financial problems, did not attend the meeting on Saturday at the Spanish Grand Prix.

The teams are concerned by the effect Mosley's continued presence as president of governing body the FIA is having on the sport.

Most significant, though, is Ecclestone's willingness to sign the letter.

Todt is said to be "locked on" to be the next FIA president

The F1 teams have no direct influence on Mosley's position, but Ecclestone is a long-time associate of Mosley, and hugely influential in his role as an FIA vice-president.

Publicly, Ecclestone has said the allegations are no-one's business but Mosley's.

But if Mosley has lost Ecclestone's support it is difficult to see how he can survive.

One source told BBC Sport that Ecclestone told the team bosses that former Ferrari sporting director Jean Todt was "locked on" to replace Mosley, it was just a question of how quickly they wanted him in.

A number of the FIA's member automotive clubs have called on Mosley to go, and four of the car manufacturers in F1 have demanded a response from the organisation.

Mosley has called an extraordinary meeting of FIA members for 3 June, where he will face a vote of confidence.

He will try to convince them that he is capable of carrying on his role, and that the allegations by the News of the World amount to an illegal invasion of privacy.

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He has launched legal action against the newspaper.

But Mosley's ability to effectively perform his role continues to be questioned by those in F1.

He did not attend the Spanish Grand Prix this weekend despite it marking the launch of the FIA's anti-racism campaign.

Instead, he chose to attend the inaugural Jordan round of the world rally championship, where the Jordanian royal family made it clear it would not be meeting him.

At the same time, Jordan's neighbour Israel withdrew an official invitation to the 67-year-old after learning of the recent scandal.

Mosley has said plans to attend the Monaco Grand Prix next month.