The MP for Dagenham is the latest in a string of Labour figures to endorse the former Mayor of London's candidacy for the 2012 election -- including Tottenham MP David Lammy as campaign chairman and London MEP Claude Moraes.
London party members and associated organisations will vote on the candidacy at Labour's annual conference in September, with the result declared on September 24 -- two days after the selection of Labour's new party leader.
Cruddas -- who became a Labour MP in 2001 after working for 10 Downing Street -- said Labour needed a candidate who could "unite the party".
He said: ?London has faced economic upheaval in recent years, and will soon come under serious attack from the national government as it imposes a series of devastating cuts on the services Londoners rely on.
?The Mayor of London can play a big role in defending Londoners from these cuts, and building an alternative to the Conservative agenda."
After coming third in the 2007 deputy leadership race, Cruddas was tipped to run as a Labour leadership candidate after the party was ousted in the May elections, but he ruled himself out of the contest.
"Labour needs a candidate who will be a first-rate mayor from day one, who knows the levers of power, and how to use power in the interests of all Londoners," Cruddas added.
?For me, Labour?s candidate must be Ken Livingstone. He has my vote, and I call on all Labour members to unite behind him too."
Livingstone welcomed the endorsement, saying: ?Jon has established a distinctive and influential voice in the Labour party and I?m delighted to have his support today which is a great new boost to my campaign to be Labour?s candidate."
Livingstone lost the 2008 mayoral election to Boris Johnson, after eight years in office.
Source: AFP European Edition