Jenson Button's hopes of a 10th season in Formula One suffered a new blow today after Sebastien Bourdais was confirmed as Toro Rosso's second driver.

With the participation of Button's Honda team in this year's world championship still far from certain, filling the vacancy at Toro Rosso was seen as the Briton's last chance of definitely making the starting grid.

As the other nine teams have named their drivers for the season, Button's hopes rest with a proposed management buy-out of Honda, whose parent company quit Formula One in December as a consequence of the global financial crisis.

Honda team principal Ross Brawn and chief executive Nick Fry are trying to attract new investment and sponsorship but they are working against the clock with the opening Grand Prix in Australia just seven weeks away.

FIA president Max Mosley said: "They may succeed. They are very competent people. Talking to people around the team, they seem optimistic. But they always are until the moment comes."

Button has had one win from 153 races, triumphing at the 2006 Hungarian Grand Prix.