One of the biggest trade unions has decided to support Jeremy Corbyn as leader of the Labour Party.
The Communication Workers Union backed Mr Corbyn, having supported him in last year's election.
The CWU has around 200,000 members in the Royal Mail, Post Office, BT and other firms.
Mr Corbyn has already received the support of unions including the train drivers' Aslef and construction workers' Ucatt.
CWU general secretary Dave Ward said: "We need a fundamental change in Labour politics and Jeremy Corbyn recognises this. He is the candidate to drive through the change that ordinary people are crying out for - opposing damaging austerity measures and tackling the housing crisis which is causing misery for so many.
"It's policies like Jeremy's announcement on extending the recognition for trade unions which we believe will make a real difference to the working lives of millions.
"Jeremy is a leader for the millions, not the millionaires, and the CWU is proud to support him."
Mr Corbyn told a meeting of CWU activists that a Labour government would tackle the "injustices" in UK workplaces, such as banning zero-hours contracts.
He also pledged to increase the living wage and repeal the controversial Trade Union Act which places restrictions on strike ballots.
"Are we to sit back and let the rich get richer? It is time to end rip-off Britain," he said.