Nov. 7 (Bloomberg) -- Paul Drayson, a member of the upper house of the U.K. Parliament, quit as an unpaid defense minister to take part in the American Le Mans sports-car racing series.

Drayson, responsible for buying military equipment, wrote to Prime Minister Gordon Brown today saying he is taking a ``leave of absence'' after qualifying for the 24-hour race in 2008 in a British championship this year. He drives an Aston Martin fueled by bioethanol, a gasoline substitute made from crops.

``A number of special circumstances have now presented me with a once-in-a-lifetime opportunity to take my racing to the next level,'' Drayson, 47, wrote in the letter released by Brown's office in London. ``For the first time next year, the American Le Mans Series will allow bioethanol cars to compete, and so this is a wonderful opportunity to showcase British motorsport technology for environmentally friendly racing.''

Brown replied that he looked forward to Drayson's return to government and wished him ``all the very best of luck with the racing.''

Drayson, a donor to the ruling Labour Party, retains his position as a lawmaker in the House of Lords. His job as defense procurement minister went to Ann Taylor, another member of the Lords.

Drayson, who has a doctorate in robotics and was chief executive of PowderJect Pharmaceuticals Plc until he sold the company in 2003 to Chiron Corp., has been a minister since May 2005. He gave 500,000 pounds ($1.05 million) to Labour before the general election that year, according to the U.K. Electoral Commission.

Iraq, Afghanistan

Drayson oversaw the deployment of Typhoon fighter jets and Mastiff mine-protected vehicles in Iraq and Afghanistan. Typhoon jets are made by BAE Systems Plc. The Mastiff is a six-wheeled armored vehicle made by Force Protection Inc., based in Ladson, South Carolina.

``The only minister with any credibility in the defense industry has now abandoned ship,'' Liam Fox, opposition Conservative Party spokesman on defense, said in an e-mail. ``There will now be no one with any defense industrial experience within the Ministry of Defence's ministerial team.''

BAE Systems Chief Executive Officer Mike Turner said in a statement he regretted Drayson's departure.

``He has done a great job in establishing a much needed defense industrial strategy,'' Turner said. ``It is very important that the direction that he has set is maintained.''

Drayson lists another of his recreational interests as sword fencing.

To contact the reporter on this story: Kitty Donaldson in London at kdonaldson1@bloomberg.net.

Last Updated: November 7, 2007 11:01 EST