Jeremy Corbyn backed by another trade union, the CWU

The Communication Workers Union (CWU) is the latest group to back Jeremy Corbyn as the next leader of the Labour party.

Conservatives, Greens and other hard left supporters are feared to have been exploiting new rules brought in by Ed Miliband which allows them to pay £3 to become “registered supporters” and have a say on the leadership race.

She added: “We have got a very, very detailed verification process of listening in to phone calls to make sure that when people are signed up to be an affiliated supporter that they are people who support the Labour party”. We actually put that principle of loosening their grip on this party once and for all as more important than the actual leadership qualities of any of the candidates standing, and we think Jeremy will lead that debate and out of that you will see a very different Labour party.’. Whether Corbyn wins or loses, none of this bodes well for the future cohesion of the Labour Party.

CWU general secretary Dave Ward said: “We reject the notion that Labour needs to move to the centre ground of British politics”. The Centre ground has moved significantly to the right in recent years.

“Jeremy agrees with the vast amount of CWU policy, ranging from opposing the selling off of Royal Mail, to offering a real alternative to austerity, and repealing anti-trade union laws”. That would deny the three other, more moderate candidates, Andy Burnham, Yvette Cooper and Liz Kendall, of the chance of winning in a second round based on second-preference votes.

Mr Corbyn started out as a rank outsider but has since won significant endorsements, including the backing of Unison, one of the country’s biggest trade unions.

But Ms Harman said detailed checked were being carried out on new supporters, including monitoring their calls.

“We know a lot of people are skeptical about the Labour Party, for many very legitimate reasons”.

Labour membership is expected to by 66,000 higher than on May 8.

Prominent individuals to sign the letter included former Guantanamo Bay inmate Moazzam Begg and 92-year-old anti-war activist Walter Wolfgang, who was famously ejected from the 2005 Labour Party conference after he heckled then-Foreign Secretary Jack Straw over the Iraq war.