John Prescott, deputy prime minister to Britain's Tony Blair during his 10 years in government, has died aged 86 after a battle with Alzheimer's, his family said on Thursday.

Prescott, who served under Blair from 1997 to 2007, was known as a plain-speaking politician who bridged the divide between the traditional left-wing and the modernisers in the Labour Party.

Dubbed an old-school political "bruiser", he famously punched a member of the public during an election campaign in 2001, after he had been hit by an egg.

"Of course, it would have all been better if it hadn't happened," Blair said at the time. But added: "John is John".

Prescott was born on May 31, 1938, in a seaside house in Wales. His father was a railway signalman, his mother a maid.

Aged 17, he went to sea as a steward on a luxury cruise ship where boxing bouts were organised among the crew to entertain the passengers.

He went into politics after coming ashore and he attended Oxford's Ruskin College, which offered courses for mature students.

Prescott entered parliament in 1970 and worked his way up the ranks, becoming a key player in the Labour Party's historic three election victories from 1997 to 2007.

He acted as a peace broker in the often fraught relationship between Blair and his future successor, Gordon Brown, and was later called "Two Jags" after he used his ministerial car for a 200 yard journey, which he said was needed to prevent his wife's hair from being blown about in the wind.

Blair said he was devastated by the news.

"He was one of the most talented people I ever encountered in politics; one of the most committed and loyal; and definitely the most unusual," he said. "There was nothing about John which fitted conventional wisdom."