Lord Sainsbury has resigned from his role as science minister, citing personal reasons.
The life peer said he was stepping aside from government to concentrate on other interests.
He will still carry out a review of science and innovation policies across government for the chancellor and other ministers, due in the summer of 2007.
"After eight enjoyable years as minister of science and innovation in the Department for Trade and Industry (DTI), I believe this is the right moment to take up again my business and charitable activities," he said today.
"I look forward to continuing to support the government with the review and in the House of Lords."
Tony Blair said the government owed Lord Sainsbury a debt of gratitude and praised his work as science minister.
"David Sainsbury has been a valued colleague, for whom I have the highest regard. He has been a huge asset to this government and the country," the prime minister said.
"David has worked tirelessly to push the case for science within government.
"It is in no small part down to him that this country's science base is in better shape than for decades - something of vital importance for this country's future.
"His contribution to government will have a huge impact in future decades and we owe him a real debt of gratitude."
Lord Sainsbury was appointed science and innovation minister in July 1998. He became a life peer in September 1997, shortly after Labour came to power.
Malcolm Wicks is taking over as science minister, with Ben Bradsure promoted to minister of state, Labour peer and former MEP Lord Truscott has become a parliamentary under secretary at the DTI, and Alistair Darling has taken over sole responsibility for energy policy.