Labour leader Jeremy Corbyn should be “given a chance” and allowed 15 months to prove he can turn around opinion polls, says union boss Len McCluskey.

The general secretary of Unite said Mr Corbyn was being “slaughtered” by the media for putting forward policies to build a “different… better Britain”.

He said Mr Corbyn himself would want to look at the party’s direction if there was no change within 15 months.

Mr Corbyn says Labour is ready for a general election if one is called.

He has twice been elected party leader on a landslide of votes from party members but has faced opposition from many of his own MPs and a mass walkout from his front bench last year.

‘Slaughtered by media’

The party has recently suffered defeat in the Copeland by-election – a seat it had held for more than 80 years – and poor poll ratings has led the Fabian Society think tank to warn the party is on course to win fewer than 200 seats for the first time since 1935 at the next general election.

The latest Guardian/ICM polling figures suggest the Conservatives have a 19-point lead over Labour.

Mr McCluskey, whose union is Labour’s biggest financial backer, told BBC Radio 5 live’s Pienaar’s Politics that Mr Corbyn was a “decent man” who had upset the establishment by putting forward “alternative” policies for a “fairer” Britain and had been “slaughtered unmercifully” by the media since becoming leader.

Pressed on whether Mr Corbyn could take Labour to victory in the next general election, he said: “The reality is that I’m hoping that he’s given an opportunity to put the alternative that Labour are building to the British electorate and hopefully we’ll see if he can break through and the opinion polls begin to change.

“I would suggest that the next 15 months or so will give us the answer to that. “

“I think it will give us an answer. In the meantime Unite as we always do – because we’re the biggest affiliate – will support the Labour Party.”

‘We are ready’

He added: “Please give him a chance… I believe that there is a chance that [things can turn around].”

He said Mr Corbyn “doesn’t have an ego, he’s not on a power trip”. The Labour leader “himself would be involved in debates and discussions about where the party’s going” if, after 15 months, there was no change.

But asked what he would do if Mr Corbyn had not made a significant impact within 15 months, he added: “You have been at me for months and months to come up with timescales – I’m not going to do that.”

The Labour leader appeared on ITV’s Peston on Sunday and said the party would not block a government bid to repeal the Fixed-term Parliament Act – allowing a general election to take place before 2020.

He said: “We are developing our policies but clearly if an election is called we can bring all that forward and we are ready, yes… We would not block it, of course not, because if that’s what is on offer, I don’t know if that’s in [Prime Minister Theresa May’s] mind or not.”

Mr McCluskey has been involved in a row this week with his former flatmate – and Labour’s deputy leader – Tom Watson, who has said Unite has plans to pump cash into left-wing campaign group Momentum, which Mr Watson says would threaten Labour’s existence “as an electoral force”.

Mr McCluskey told Pienaar’s Politics there had been a “shameful campaign of lies, innuendo and smears”, warning: “It strains the relationship between unions and the Labour Party.”

He is up for re-election at the end of next month and those close to Mr Watson are believed to see it as an opportunity to weaken both him and the current party leader. His main opponent is the West Midlands organiser Gerard Coyne, who is politically to his right.