The Prost formula one team filed for bankruptcy in the French courts yesterday and is poised to become grand prix racing's most high-profile casualty since Lotus in 1994.

But the owner, Alain Prost, four times world champion at the wheel, pledged to fight back to solvency and save his 250-strong workforce at its factory at Guyancourt, near Paris.

"Everything will depend on the offer we receive," he said. "What we need is a big sponsor. That's what we've been missing from the start."

A receiver has been appointed for the next six months with a view to selling the team or disposing of its minimal assets to defray debts estimated at £21 million sterling.

There is speculation that a consortium of venture capitalists are interested in buying it.

"Anybody interested in buying Prost would just have to take on the debts because the team itself is worth nothing," said one well-placed formula one insider yesterday.

He estimated that television rights would bring in about $10 million next season and the new factory at Guyancourt might be worth $5 million. "But with that amount of debt it's going to be difficult to move," he added.

The former Prost team driver Pedro Diniz and his father Abilio, the Brazilian supermarket tycoon, last year took 40 per cent of the shareholdings. Prost later rejected their offer to buy the team for a nominal dollar.

Yesterday Daniel Morelli, Diniz's spokesman, said the family was no longer interested in taking over.

The Prost team entered Formula One in 1997 but has failed to make any significant steps forward in its four-year existence. After picking up 21 points in its debut season, the team managed just one in 1998, nine in 1999 and none at all in 2000.

A year ago Prost believed the decision to adopt a Ferrari engine for the 2001 season would be the making of his team. But while Sauber, with the same engine, jumped from eighth place to fourth with 22 points, Prost could still only limp through the season.