They were searching for evidence of industrial espionage as part of an Italian criminal investigation into the Spygate scandal.

This had already cost McLaren a whopping £50 million (S$141 million) fine last season for illegally possessing secret Ferrari data.

The British team tried to play down the significance of the raid, which was also conducted at their Woking factory and the homes of other key personnel, including suspended chief designer Mike Coughlan.

It was Coughlan's receipt of a 780-page dossier of Ferrari secrets from Nigel Stepney, the Italian team's former mechanic, that sparked the scandal midway through last season.

However, the raids come at a very sensitive time for Dennis.

Mercedes, McLaren's largest shareholder, is putting pressure on him to step aside after his woeful handling of the Spygate furore.

In addition to the fine, the team were kicked out of the constructors' championship last season and ended up losing the drivers' title despite leading for most of the campaign.

Their reputation was heavily tarnished for cheating and then trying to cover up the theft of Ferrari data.

Spanish newspaper Marca went so far as to claim that 60-year-old Dennis, who still owns 15 per cent of McLaren, had already been fired. His No 2, Martin Whitmarsh, was expected to take over the embattled team.

The loss of Dennis could destabilise driver Lewis Hamilton's preparations for a season that starts on March 16 in Australia, not to mention the blow to team morale.

Dennis had discovered and mentored Hamilton since he was 10.

Jackie Stewart, the former British triple world champion, told The Daily Mail: 'McLaren will insist it is business as usual, but they are having to deal with all kinds of external issues, including the racist abuse Lewis faced in Barcelona.

'These matters all deflect a team from their prime concern: to put together the best car.'

Hamilton was abused by spectators shouting racist slurs and wearing dark make-up, black wigs and T-shirts saying 'Hamilton's Family' during testing on Feb 2 at the Montmelo circuit.

To antagonise McLaren further, their former driver Fernando Alonso blamed the British driver for the taunts.

That racist incident came after an interview last month in which Hamilton said Alonso showed him 'just how not to behave as a world champion' when the two were teammates at McLaren last season.

'The very next week, they whistled him in Spain for saying that,' said Alonso, a Spaniard.

But, asked if Hamilton could win the title this season, he said: 'Possibly, yes.

'After one year's experience things become easier and that will give him an advantage.'

But this does not mean he is Alonso's favourite to do so.

'If I have to name one favourite then Ferrari's Kimi Raikkonen because he is the world champion.

'He has the self-confidence and he is obviously very quick, so he has put himself in a very strong position.'

ASSOCIATED PRESS