KEIR Starmer has become the first Labour leadership contender to be guaranteed a place on the final ballot paper after winning the support of retail trade union Usdaw.

The Shadow Brexit Secretary said that if he was elected Labour leader, the party would “stand shoulder to shoulder with the trade union movement as we take on the Tories and rebuild trust with working people".

He won his place on the final ballot after adding Usdaw's endorsement to the support of Unison and the Socialist Environment and Resources Association.

Candidates are required to have won the nomination of three Labour affiliates, including at least two unions, which amount to at least five per cent of affiliate members.

The only other route on to the final ballot is by receiving nominations from at least five per cent of constituency Labour parties.

Sir Keir, who represents Holborn and St Pancras in London, said he was honoured to have received Usdaw's endorsement and said it proved his campaign was building unity across the Labour movement among trade unionists and members.

"Usdaw represents over 400,000 workers and fights every day for its members and for a fairer society. If I'm elected leader, Labour will stand shoulder to shoulder with the trade union movement as we take on the Tories and rebuild trust with working people."

The retail union also backed Angela Rayner, the Shadow Education Secretary, for the deputy leadership.

The Greater Manchester MP’s main rival for the role, Ian Murray, Labour’s only Scottish MP, was said to be having positive feedback from a number of trade unions and appeared confident about getting the support of the Community union, which represents a diverse range of sectors, including iron and steel, clothing, and textiles.

The GMB is expected to declare its support on Tuesday with suggestions it could back Sir Keir or Lisa Nandy, the Wigan MP, for the leadership.

Rebecca Long-Bailey, the Shadow Business Secretary, is expected to win the support of Unite, Labour’s largest donor, later in the week.

On Monday, the deadline passed for people to join Labour to vote in the leadership contest, which will end with the announcement of the winner and successor to Jeremy Corbyn on April 4. It is thought that some 100,000 people have joined to take part in the selection for the new leader and deputy leader.

One suggestion is that the surge is largely made up of those who wish to return the party away from the radical Left to the centre ground.