Jack Straw told a constituency meeting in Blackburn he'd been "astonishingly blessed" to represent the town and work as minister and shadow minister but that at 67 he "couldn't guarantee" he could keep up the pace required into his mid-70's.
Althoughhe backed his brother David in the Labour leadership campaign in 2010, Mr Strawpaid tribute to Ed Miliband:
"In Ed Miliband we havea leader who has the ability, the determination, and thecharacter to take this country to a better, and much fairerplace than under this Government."
More top news
His mother Princess Diana was killed in a car crash in Paris in 1997 when he was just 12 and his brother William was 15.
The 21-year-old, who was arrested on Sunday, also allegedly injured two other people in the attack in the German city of Reutlingen.
She was going to the aid of a family member who got out of the car in the middle of the park and was dragged away by a different tiger.