Britain's main opposition Labour Party on Tuesday opened nominations for candidates to replace Jeremy Corbyn as leader after a disastrous slump in support at recent elections.

Six candidates have already announced they will stand, with four women hoping to become the traditionally centre-left party's first female leader in its nearly 120-year history.

The contest is the fourth since Labour last held power in 2010. Nominations close in a week. Voting takes place from February 21 to April 2, with the winner announced two days later.

Corbyn, a veteran socialist, moved the party significantly to the left since his election as leader in 2015 but announced he was stepping down after last month's crushing election defeat.

The party haemorrhaged support across its former heartlands in northern England to hand Johnson a landslide victory, which will enable him to push his Brexit deal through parliament.

Many blamed Labour's defeat on Corbyn's leadership and ambivalent stance on Brexit.

The early favourite is Keir Starmer, the party's Brexit spokesman and a former director of public prosecutions, who is seen by some as a more palatable centrist candidate.

Other contenders include foreign affairs spokeswoman Emily Thornberry, shadow finance minister Clive Lewis, and backbenchers Lisa Nandy and Jess Phillips.

The battle is shaping up to be one for Labour's ideological soul, with several of the candidates openly critical of Corbyn, his team and the party's policies.

The direction it takes will likely determine whether Labour has a chance of preventing another possible 10 years of Tory government.

On Tuesday, Rebecca Long Bailey, widely viewed as Corbyn's heir, confirmed her candidacy, saying the party needed "a leader that can be trusted with our socialist agenda".

The party's business spokeswoman will likely win the backing of the grassroots Momentum organisation and Labour's powerful trade union backers.

"We need a proud socialist to lead the Labour Party," she said in an article for the left-wing Tribune magazine announcing her candidacy and defending the Corbyn era.

"I don't just agree with the policies, I've spent the last four years writing them," she added, in a rebuttal to critics who say Labour must abandon its more radical stances to regain power.

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Labour's Brexit spokesperson
Labour's Brexit spokesman Keir Starmer and the party's business spokeswoman Rebecca Long Bailey are among the favourites to replace veteran leader Jeremy Corbyn. Photo: AFP / Niklas HALLE'N