“I’m really excited about driving a McLaren again and to be re-engaging with the team,” said the 38-year-old Finn.

McLaren have already confirmed their driver line-up for 2007, with young Briton Lewis Hamilton to partner reigning champion Fernando Alonso.

Hamilton, whose position was confirmed last week, is currently in the second day of a three-day test programme alongside Pedro de la Rosa.

De la Rosa will make way for Hakkinen tomorrow, with the team insisting the move constitutes part of their winter testing schedule as they prepare for the new season.

Hakkinen, who has driven in the DTM Touring Car Championship for the last two years with Mercedes, added: “I have followed the Formula 1 world championship closely since my retirement.

“But it was when I was at this year’s Brazilian Grand Prix as a guest of the team that I really felt I would like to get a chance to drive a Formula 1 car again.

“I have recently spent some time in McLaren’s simulator in Woking, and to get the opportunity to drive the car is something I’m really looking forward to.

“This test is a chance for me to see how much Formula 1 cars have advanced, and experience first hand what they are like to drive today, as well as providing the team with some feedback on various aspects of the car’s performance.”

McLaren team principal Ron Dennis is adamant that at this stage such a move is a one-off.

“We are delighted to provide Mika with the opportunity to drive a Formula 1 car again,” said Dennis on Hakkinen, who won his two world titles with McLaren in 1998 and 1999.

“He is really looking forward to getting behind the wheel of a current Formula 1 car.

“A driver of Mika’s calibre and experience can only bring added value to our testing programme and his feedback after tomorrow’s running will be valuable to the team in our preparations for the 2007 season.

“However, at this stage there are no plans for Mika to conduct further tests for the team.”

Two three-day test sessions are planned at Jerez before Christmas.