Opposition: Leading Labour light Jack Straw to retire from the front bench

The Blackburn MP, who served as Justice Secretary, Home Secretary, Foreign Secretary and Leader of the Commons, said he believed Labour needed a "fresh start".

"I was first appointed to the Labour front bench in 1980, and then elected to the Shadow Cabinet in 1987," he told the Press Association. "But now I want the freedom to range more widely over foreign and economic policy."

He added: "I'll be spending more time on my constituency, and I will be writing a memoir in time."

Mr Straw said he would leave in early October when a fresh Shadow Cabinet had been appointed under a new Labour leader.

But he said he was not planning to quit as an MP.

Mr Straw, Gordon Brown and Alistair Darling were the only Labour figures to remain in the Cabinet throughout the party's 13 years in power. Mr Darling has already indicated he is retiring to the back benches.

Mr Straw entered Parliament in 1977, and was made Opposition Treasury spokesman in 1980.

Neil Kinnock promoted him to the Shadow Cabinet as education spokesman in 1987 and he took charge of the Home Office after Labour gained power in 1997.

In 2001 Mr Straw became Foreign Secretary and oversaw the fraught negotiations in the run-up to the Iraq War.

When Gordon Brown entered Number 10 in 2007, Mr Straw was made Justice Secretary and Lord Chancellor.