LONDON — Fabian Society general secretary Andrew Harrop has told Business Insider that the Labour Party has "got to sound patriotic and concerned about security" if it wants to win the next general election.

In a wide-ranging interview with BI the head of Britain's oldest left-wing think tank also said:

Corbyn must "reach out" to socially conservative voters as " Labour is not going to win more seats by appealing to even more liberals."

The party can win an election with left-wing economic policies, but only if they "look like you know how to run the country"

Labour must not "shatter its own coalition" by campaigning for Britain to stay in the single market.

MPs should only be considered for deselection if they are doing "a terrible job" and party members should listen to constituents.

BI spoke to Harrop at the Fabian Society's summer conference entitled 'Path to Power' in central London where the centre-left think tank hosted a "crucial discussion" on the future of the Labour Party. The conference took place a month after the June general election when Labour upset polls and expectations to gain 30 seats.

The Fabians had previously predicted that Labour would drop to fewer than 150 MPs in last month's election, saying they were "too weak to win and too strong to die."

Speaking about the future of Labour, he said that the party leadership has to reach out to Brits with socially conservative views as well as those with socially liberally beliefs, in order to build a "coalition" of support.

"I think you can be a left wing radical leader but you've got to have a very different style — you've got to sound patriotic, concerned about security and concerned about reciprocity," Harrop said.

Corbyn's opponents have previously accused him of not being proud to be British. Corbyn was widely criticised afterfailing to sing the national anthemat a Battle of Britain memorial service in 2015. He is also a lifelong opponent of Britain's nuclear deterrent.

Harrop was keen to stress, though, that he believed Corbyn's left-wing economic policies can appeal to a sufficient number of voters to win a general election.

He said: "You've got to look like you know how to run the country, [and be] reliable in terms of economics and fiscal [policy].

"None of that means you can't be left wing."

He added: "Labour did ok with left-leaning social conservatives but not good enough. The challenge is really to be the party for everyone with left-leaning economic views, including people who are more socially traditional."

Harrop rejected claims that Labour only offers "a policy package for urban liberal graduates" and insisted that the party "still has lots of people voting for it who you would call social conservatives."

However, the party must "reach out" to more people if it is to win an election, he added.

"The challenge is how do you move forward and Labour is not going to win more seats by appealing to even more liberals," he said.

The Fabian Society, dating back to 1884, is one of the UK's oldest political think tank and a founding organisation of the Labour Party. Harrop said: "I think we're a useful bridge building organisation in a fairly polarised space... the Fabians have a massive role in bringing people together with different politics."

Labour must support leaving the single market

Fabian Society general secretary Andrew Harrop Fabian Society

Last month 49 Labour MPs rebelled against Corbyn to support an amendment tabled by colleague Chuka Umunna calling for Britain to stay in the single market after Brexit. However, Harrop told BI that he does not think Labour should be campaigning for single market as it could "shatter" the coalition of support it has built up.

Labour campaigning to stay in the single market "would shatter its own coalition... lose its own Leave voters. It would be accused of defying the will of the referendum and being anti-democratic," Harrop said.

He didn't rule out the possibility altogether, though, explaining that Labour could adopt a pro-single market position in the future if public opinion eventually turns against what is commonly dubbed a "hard" Brexit.

Harrop said: "I do think that the best outcome for Britain is a very soft Brexit which is either single market membership or something pretty close to it... I think you can only get there once public opinion has started to move.

"Labour is going to have to follow public opinion as well as lead it — you can't say the answer is staying in the single market before people have understood the problem. The focus of the party has got to be about exposing the problem [of Brexit] so people are really worried about it. It is starting to happen but most people aren't engaged in the detail, they're not worried about 20-mile queues of lorries at Dover."

Labour MPs should only face deselection if doing a "terrible job"

The question of party unity within Labour has been thrust into the spotlight following reports that members of Labour MP Luciana Berger's local branch have told her to apologise for not being more supportive of Corbyn's leadership.

Deselection has been a prominent issue since Corbyn took over. The Labour leader has not ruled out the possibility mandatory reselection of Labour MPs — an event that moderates fear would lead to a left-wing take over of the party.

Discussing the issue of deselection, Harrop claimed: " If a Labour MP is doing a terrible job, there is a structure there to deselect them.

"If local parties feel so strongly about the performance of their MP they should use that structure. It has been deliberately set up — a threshold that is not unobtainable but is quite hard."

He uses the example of Kate Hoey, the Brexit campaigner who is MP for Remain-voting Vauxhall, to show that an MP might be disliked by party members and her local party, but is still popular with voters and so has not been removed.

Labour MP Kate Hoey (left) campaigning for Brexit alongside Nigel Farage. Jeff Spicer / Getty "It's not to say that you should never consider deselection but that it should be weighed up very carefully and particularly thinking about the views of constituents in that seat rather than just members," he said.

He admitted that he expects the threat of deselection to become a more common feature of Labour politics going forward."It's possible that we'll see more local parties at least threatening to use trigger ballots to deselect MPs.

"But members should bottle the spirit of the campaign we've just seen where they work together and it's team Labour and all sides having a bit of respect and comradeship.

"That is going to involve MPs spending more time with their active members than they might have in the past. If they are building up good relationships, and if they're all out campaigning together small differences on policy views are far less important."

"The Conservative party will do everything in its power to cling on"

Harrop isn't convinced that another general election is just round the corner. "Just having had one snap election after a new leader and seeing what a disaster that was, I think the Conservative party will do everything in its power to cling on, even with a new leader," he said.

"It feels like John Major's government, where you feel they're completely ground down. But Major went all the way... so I think chances are you're going to have a Conservative government of some sort for five years even if it's a lame duck."