Livingstone saw off a challenge from former MP Oona King to secure 68.6% of votes in a ballot of Labour Party and trades union members in the capital.
The result of the ballot was announced this morning at the Coin Street community centre near London’s Southbank.
After the result Ms King vowed to support her former opponent and said the party was “united” behind him.
Livingstone’s widely expected victory formalises his candidacy after more than two years of commenting on, and campaigning against, his successor’s policies since losing office in 2008.
Speaking this morning Livingstone sought to characterise his successor’s regime as “disastrous” for Londoners and said attempts by Mr Johnson to distance himself from the coalition’s cuts were “a con trick” and claimed Johnson had actively campaigned for a Westminster government he “knew” would make cuts.
The defeat of King will disappoint many in the Labour party who argued it was time for the party to “move on” and present a different face and agenda to the capital. It also means Livingstone will have contested each of the four Mayoral elections held since 2000.
Despite enthusiastic endorsements by 7 of the 8 Labour members on the London Assembly and 17 MPs, Livingstone has faced criticism for failing to offer a radically different set of policies than those contained in his 2008 manifesto.
During the selection contest Livingstone, who in 2008 proposed a £25 congestion charge for the “most polluting” vehicles, has said he still favours emissions-based road charging and has vowed to re-introduce the Western Extension of the Congestion Charge Zone which Mayor Johnson intends to scrap this December.
However senior supporters insist the former Mayor has “learnt to listen” to voices outside his “usual circle” of advisors.
In recent weeks Mr Livingstone has announced policies “to bring greater equality” for Lesbian, Bisexual, Gay and Transgendered Londoners including by creating an LBGT Mayoral advisor and has also vowed to promote the music industry in the capital.
Livingstone’s campaign team insist further new policies will be announced in the coming months.
Incumbent Mayor Boris Johnson has already declared his intention to seek re-election. Of the parties currently represented within the Greater London Authority, the Liberal Democrats and Greens have yet select a candidate.
