Labour leadership contender Ed Balls has received a boost to his campaign after he was given the support of the Communication Workers Union, the union which represents postal workers and staged a series of strikes last year against changes made by management at Royal Mail.

Until now Balls has been seemingly lagging in the campaign, despite a strong media presence. He still has the fewest nominations of any of the five candidates even compared to supposed outsider Dianne Abbott.

So far Abbott has secured the support of two of the 14 trade unions affiliated to the Labour Party, as well as at least 12 Constituency Labour Parties.

By contrast Balls has only six CLPs declared for him and now one trade union.

The contest is currently being dominated by brothers David and Ed Miliband who between them have the support of 12 of Labour's 13 MEPs and a sixth of all CLPS.

David Miliband also has the support of the USDAW and Community Unions while Ed Miliband won something of a coup last week when the powerful GMB Union threw its support behind him.

Andy Burnham also has a significant following with 17 CLP's declared for him so far as well as Labour's remaining MEP and the National Union of Labour and Socialist Clubs.

Balls, despite his lack of nominations, has been prominent in the headlines in recent weeks due to his role as Shadow Education Secretary in which he has challenged Conservative Education Secretary Michael Gove for bungling a list of schools that were being saved from the scrapping of the Building Schools for the Future programme.

The CWU General Secretary, Billy Hayes, said that Balls "has a sense of purpose and vision that can rebuild the Labour Party. He values the contribution that trade unions make to the country and to the Labour Party. We also believe that he is tough minded enough to lead the country and are certain that he is the right leader for Labour."

In response to the nomination Balls said, "I'm honoured to have received the CWU's nomination following this week's hustings and the recommendation they will make to their members in the one member one vote ballot in September. I want to strengthen Labour's link with the trade unions - not just nationally, but on the ground in every constituency and union branch. That is the best way for Labour to stay in touch with millions of working people who depend on Labour to stand up for them."