UPDATE 16.38: Jeremy Corbyn has this afternoon reportedly secured the endorsement of a fourth trade union, the RMT. Again, the union is not affiliated to Labour, so it will be interesting to see how these endorsements work practically. Will they be encouraging their members to sign up as Labour supporters for £3 in order to vote?

A third trade union has today given Jeremy Corbyn their endorsement in the race to become next Labour leader. The Fire Brigades Union (FBU) has today said that Corbyn is the “obvious choice for trade unions.”

However, the FBU disaffiliated from Labour in 2005, meaning that their members will not be entitled to a vote unlike ASLEF and BWAFU, the two other unions supporting Corbyn. A fourth union, the TSSA, made an intervention during the nominations process to call on MPs to ensure Corbyn made the ballot, but stopped short of giving him their official backing.

In a statement announcing their decision, FBU general secretary Matt Wrack said: “The FBU is not affiliated to the Labour party but the question of who leads Labour is obviously of great importance to all workers.”

Wrack said that Corbyn was the “natural choice” and believe he would renew investment in public services:

“We hope that under his leadership we would see a shift in focus away from the accumulation of wealth for the few, towards policies for the majority.

“We need to see investment in essential services from a leader who values and supports public sector workers, who isn’t willing to continue the game of Russian roulette that has been played with public safety since 2010 through unprecedented cuts to services and jobs.

“We believe Jeremy Corbyn is the right person to do that.”

It is also expected that the RMT, who were expelled from Labour in 2004 following a decision to give funds to the Scottish Socialist Party, will soon take a vote on whether they will back a candidate.