28/09/2015 16:20 BST | Updated 02/10/2015 16:59 BST

Dan Jarvis Warns Coming Elections And By-Elections Will Be 'Major Test' For Jeremy Corbyn's Leadership

Dan Jarvis has warned that next year’s local, Scottish and London mayoral elections will be a ‘major test’ for Labour under Jeremy Corbyn’s leadership.

The former shadow justice minister said that future by-elections would also test the party’s ‘instinctive’ loyalty, and suggested that Ed Miliband would have been under huge pressure to quit if it had lost Heywood and Middleton to UKIP last year.

Speaking at a HuffPost UK fringe event at the conference in Brighton, the ex-Army Major said that although Mr Corbyn had a huge mandate from Labour members, ‘ultimately’ politicians were judged by the electoral verdict of voters.

In a wide-ranging question-and-answer session, he said that he had been ‘incredibly humbled’ by calls for him to run for leader after the May general election but stressed he’d put his young children first and “I stick by that decision”.

Mr Jarvis made his remarks as Tristram Hunt also appeared to set the clock ticking on the Corbyn leadership, warning of the damage that would be caused if Labour lost the London mayoralty election next year.

The former Paratrooper, who is still seen by some in his party as a future Labour leader despite not being invited to join the Corbyn shadow team, said that “now that I'm on the backbenches I think I've got a greater opportunity to speak my mind”.

Asked if Labour should have removed Ed Miliband before the general election, he replied: “I think it is a good thing that we are instinctively loyal as a Labour Party, as a Parliamentary Labour Party.

“But in the end politics has got to be about giving our party the opportunity to change this country for the better using our values. It is a Labour Prime Minister, it is a Labour government that we have got to work towards.

“We should never lose sight that it's got to be rooted in the lives of people we want to represent.”

And asked if the true test of any leader and party was at the ballot box at local and even by-elections before a general election, he replied: “I think that is the case. May next year provides a major national electoral test.

“Ultimately as politicians we are all judged on elections. And we've got Mayoral elections in London, we've got elections to the Scottish Parliament, we've got police and crime commissioners elections taking place around the country, we've got local government elections [in England]. This will be a major test.”

Shadow Culture Secretary Michael Dugher warned earlier this month that a Corbyn victory could result in Labour losing ‘hundreds’ of council seats in England“ as voters steered away from left-wing politics.

Mr Jarvis said: “Jeremy has a massive mandate but all of us have a responsibility to get involved…and not to accept or write off these elections.”

He stressed that turning around the party’s fortunes in Scotland was “a generational project” even though Scots Labour leader Kezia Dugdale had “made a fantastic start”.

But Mr Jarvis suggested that Mr Miliband could have been in real trouble as Labour leader if it had not won the Heywood and Middleton by-election in October 2014, by a wafer-thin majority of 617 votes.

Asked if Miliband would have been forced to quit if the seat had been lost to UKIP, he replied: “That's a very interesting 'what if'..

“We have an excellent MP there in Liz McInnes. But we were lucky that they invested all their resources into Clacton, which to be honest they were never going to win.

"If they had been smarter about it they would have pulled their people out of Clacton and ploughed all their resources in to Heywood and Middleton.

“If the Heywood and Middleton by-election had taken place a week later, I think we might have lost it. That would have put a lot of pressure on Ed Miliband. As a party it took us too long to grapple with UKIP.”

Mr Jarvis, who conducted a review of UKIP switchers from Labour for Andy Burnham’s leadership campaign, added: “There are millions of people who voted for UKIP, many of them were people who previously supported the Labour party. All of us have a job to do to convince those people”.

Labour had failed to ‘renew ourselves’ in office and should not be ‘too surprised’ that that it had not connected with many voters, he said.

Tristram Hunt echoed the point about next May's elections at a separate fringe, declaring: "It will be us heading towards mid-term territory, a government that has been in power for six years.

"There will be discontent. London is a Labour city, we hope – we always say that, it doesn’t always elect Labour mayors. So I think quite rightly there is expectation on the leadership to deliver and deliver successfully next May.”

Referring to his decision not to contest the leadership in May, Mr Jarvis said he had decided to put his young family first, despite the avalanche of calls and emails from supporters urging him to stand.

“I was incredibly humbled by the support that there was that day or so after we lost the general election.

“I thought about it, I discussed it with my family, but to be honest it was never something that was really on the table.”

He pointed out that his two older children had lost their mother to cancer in 2010.

“My older son and daughter had had a really tough time. They had lost their mum and I didn't want them to lose their dad. So I was always very clear in my mind, and I came out and said so early on.

Asked if it would be fair to characterise his stance of the leadership as ‘never say never, he replied: "I made absolutely the right decision and I stick by that decision. It was the right decision for my family. I'm pleased I took that decision.”

A former leader of a Special Forces Support Group unit in Afghanistan, Mr Jarvis said: “The hallmark of a good leader is surrounding yourself with people who are better than you.”

But he made clear that he had not expected to be given a shadow post by Mr Corbyn given their big differences on defence and foreign policy.

"I wasn't expecting to get the call and as it happened I was right,” he said. “I had specific concerns about Europe. Nato has underpinned our security in Europe, it's incredibly important.

“We now have more clarity about our position in the European Union. There were a number of fundamentally important questions that I wanted him to answer before serving.”

"I will seek to make a contribution to the party in the best way I possibly can…

Now that I'm on the backbenches I think I've got a greater opportunity to speak my mind.”

Put to him that to some Labour activists he was ‘no more’ than an excellent CV, he replied: “If I was to define my politics it's about social mobility. When I was in the army I saw young people do the most exceptional things.

"There's a part of my constituency called Kingston, I want the daughter of a cleaner in Kingston to get the same life opportunities as the son of a barrister in Kingston-upon-Thames. I think that's what we are about as a party, that's certainly what I'm about as a politician."