Defence minister Lord Drayson is taking a leave of absence from the government, Number 10 has announced.

The prime minister's spokesman said the former business chief was taking time off to compete in an American motor racing series.

Baroness Taylor, a former chief whip in the Commons, returns to government as parliamentary under-secretary for defence equipment.

And it was also announced that Lord Bach is returning to government as a whip who will speak on business issues.

Business minister Pat McFadden takes over the responsibilities that Lord Drayson had in the Department for Business, Enterprise and Regulatory Reform.

Lord Drayson, who will be taking part in the American Le Mans series, told the prime minister he had a "passion for motor racing".

His letter to Gordon Brown said that "over the past year, I have competed in the British GT championship, racing a unique bio-ethanol fuelled race car, achieving an 'historic first' win for a green-fuelled car coming second overall in the championship".

"A number of special circumstances have now presented me with a once in a lifetime opportunity to take my racing to the next level."

The successful businessman added that it would be "a wonderful opportunity to showcase British motorsport technology for environmentally-friendly racing".

He explained that "unfortunately, it cannot be combined with the challenge of full-time government office".

Responding, the prime minister paid tribute to the peer's achievements as a minister.

"I understand your desire to take up the extraordinary opportunity which has now emerged to achieve your great life's ambition," said Brown.

"I accept reluctantly that it would be impossible to do so and continue in government, given the commitments you bring to everything you do."

Lord Drayson will remain on Brown's 'business council for Britain'.

And the prime minister told the peer that "while I am sorry to lose you, I look forward to your return to government when your leave of absence ends".

Lord Drayson said he would be "delighted" to have the chance to serve again.