McLaren Mercedes stunned Formula One last night by making a grovelling apology to the FIA, motor sport’s governing body, in a humiliating bid to avoid further sanctions over their use of technical secrets from Ferrari that could harm Lewis Hamilton’s bid for the 2008 World Championship.

In a letter to Max Mosley, the president of the FIA, and the World Motor Sport Council (WMSC), which has already handed McLaren a £50 million fine for cheating, the team admitted that Ferrari technical information had penetrated farther into the team than they had acknowledged.

The admission by Martin Whitmarsh, the McLaren chief operating officer, came after he and Ron Dennis, the team principal, had seen the latest report compiled by FIA investigators into whether the team’s car for 2008 has been “contaminated” by Ferrari knowhow. Within hours of publication of the letter on the official McLaren website, it became clear that its disclosure was part of what amounts to a “plea-bargain” deal with the FIA to bring the investigation of McLaren to a close.

After the letter appeared, the FIA released a statement by Mosley in which he recommended that, in the light of McLaren’s admissions and “in the interests of the sport”, the WMSC should treat the matter as closed. The council had been due to reconsider the issue at a meeting on February 14 and could have imposed further heavy sanctions, which might have derailed Hamilton’s second season in Formula One before it had started. This will no longer happen.

The FIA denied that it had let McLaren off the hook or that recent criticism by leading figures in the sport — among them Sir Jackie Stewart, Damon Hill and Martin Brundle — that it was conducting a witch-hunt against McLaren had weakened its resolve. It said that the huge fine levied against the team, and the decision to throw them out of this year’s constructors’ championship, was vindicated by the latest disclosures and that it did not wish to damage the sport by going ahead with more sanctions.

The report by the FIA’s technical inspectors into the 2008 car contains claims that secrets leaked by Nigel Stepney, the former Ferrari mechanic, to Mike Coughlan, the technical director subsequently dismissed by McLaren, were discussed not only by Fernando Alonso and Pedro De La Rosa, the drivers, but by senior managers and engineers at McLaren.

It suggests that the existence of a McLaren “mole” within Ferrari was known to some managers at the team headquarters in Woking, Surrey, and that one area of technical development on the car was stalled until such time as the FIA ceased its investigation. An FIA source told The Times: “It is safe to say engineers and senior managers were aware of things in a way not disclosed to us previously.”

Although in his letter Whitmarsh does not accept that the car is influenced by Ferrari, this sits uneasily with his offer of a self-imposed moratorium on its development in three areas — the “quickshift” gearbox, the “fast-fill” fuel intake and the use of CO2 in tyres — in a bid to bring the FIA’s proceedings against the team to a halt.

“We would respectfully suggest, however,” Whitmarsh writes in a paragraph inadvertently published in full by McLaren, “that despite our embarrassment that pieces of Ferrari information may have penetrated our organisation beyond our previous belief, the inspection has not reached any conclusion that McLaren used Ferrari confidential information on the 2007 or 2008 car (subject to issues as to the deployment of quickshift, fast fill, or CO2 as a tyre gas for 2008, in respect of which see below).”

What is most striking about the letter is its tone of apology. It is clear that McLaren have accepted that only by this form of public humiliation can they free themselves from an episode that has seriously damaged their reputation and called into question the credibility of Whitmarsh and Dennis.

Tale of two spies

July 4 FIA launches investigation into Ferrari-McLaren spy scandal

July 26 McLaren escape punishment from World Motor Sport Council because of lack of evidence

Sept 13 After case is referred to FIA’s Court of Appeal, McLaren fined £50 million and thrown out of constructors’ championship

Sept 17 McLaren consider complaint against Renault about “use of technical information”

Nov 8 While inspectors visit McLaren headquarters in Woking, Surrey, to examine design for next year’s car for evidence of Ferrari technology, FIA summons Renault to answer charge before WMSC of possessing confidential McLaren technical information

Dec 6 Renault found guilty of the charge, but escape without punishment

Lewis Hamilton’s team-mate at McLaren Mercedes next season will be Heikki Kovalainen, The Times understands. The Finn, who finished seventh in his rookie season as Renault’s second driver, was replaced in the French team by Nelson Piquet Jr this week. Signals emanating from McLaren suggested that the team would seek to promote from inside to find the successor to Fernando Alonso, who left to return to Renault, but Kovalainen, 26, is believed to have been given the green light.