Yvette Cooper in Labour split warning over possible Jeremy Corbyn victory

Labour's leadership contest is polarising the party and could lead to a split if Jeremy Corbyn wins, rival Yvette Cooper has warned.

The shadow home secretary said the left-winger, who has voted against Labour more than 500 times, has "not shown any ability" to be part of a team as she raised the prospect of a fracture in the party if he takes the top job.

As the race becomes increasingly bitter, figures on the right of the party are reportedly preparing their opposition to the radical if he succeeds Ed Miliband through a group dubbed "the resistance".

Mr Corbyn's supporters, meanwhile, said the British political class is "frozen with fear" at the prospect of his victory and claimed a smear campaign is under way to stop him.

Ms Cooper told BBC Radio 4's World at One programme she would "always be part of the Labour party" and would not "take my bat and ball home" if the Islington North MP wins.

Asked if she was genuinely worried that the party would split if Mr Corbyn wins, she replied: "I am, because I'm worried what's happening at the moment, that the party does seem to be polarising between the different extremes and I don't think that is the right thing to do.

"Partly, we want to hold our party together in order to win. Divided parties don't win, but it's actually much more than that. I just don't think the extremes of the party are the right place to be and are true to our values and are true to the things we need to do to change the country for the future."

Mr Corbyn was yesterday forced to admit associating with Lebanese extremist Dyab Abou Jahjah after a photograph emerged of them together, but insisted he had no recollection of their meetings.

London mayoral hopeful Diane Abbott, one of Mr Corbyn's most prominent supporters, said accusations about the frontrunner's associations with extremists such as Abou Jahjah and Palestinian militant group Hamas had surfaced because opponents are terrified he will take the top job.

She told BBC Radio 4's Today programme: "The British political class is frozen with fear at the idea that Jeremy will actually win this leadership election.

"It's by no means certain, but the very notion of it terrifies people because the energy behind him has the power to disrupt and to change and transform politics.

"This is where these anti-Semitic smears come from."

Ms Abbott said opponents were "plucking" out incidents from over the course of a 30-year career and insisted MPs did not always know who they would be sharing a platform with.

She said: "If you get involved with liberation movements there will be points at which you are involved in... there will be people around who are less than savoury.

"Nobody could possibly argue looking at Jeremy's career that he is pro anti-women politics, that he is pro anti-Semitism, that he is pro anti-racism, and to try and build a case on the basis of guilt by association is very wrong and it is stopping a genuine debate about the policies that Jeremy is trying to advance in this leadership election," she added.