Last week’s election defied all predictions. When Theresa May called the snap election on April 18, who could have predicted the Conservatives would lose seats and their overall majority, and that Jeremy Corbyn – who many inside and outside Labour had written off as an electoral liability – would significantly increase his party's vote share.

In such a marginal election, where every seat counted, I think it is fair to make a bold claim. As Labour surged across London, they hit a "Jewish firewall" in four London constituencies with high Jewish population: Finchley and Golders Green, Hendon, Chipping Barnet and Harrow East.

Prominent Jewish Labour Movement campaigners fought hard and made inroads, but the swing to Labour was far more modest than in neighbouring constituencies with smaller Jewish populations. And while the results were close, they were not enough to turn these key blue seats red.

In an election as marginal as this was, four seats is a crucial number. Had the Conservatives lost the four seats they would have been unable to form a majority even with the support of the Democratic Unionist Party. Both the Conservatives and Labour should remember this as they shape their platform for the next election whether that is sooner or later.

So what lessons should the parties take from this?

For the Conservatives, it is to continue and increase its support for the Jewish community, including taking an international lead on tackling antisemitism, combating extremism and maintaining its warmth towards the state of Israel, including fighting bias at the UN and celebrating this year’s Balfour Centenary in style. Meanwhile, it should ensure that changes to the new free school programme extend provision in the Jewish community. It should also consider whether changes to welfare provision, including the two-child cap, that disproportionately hurts Orthodox families, is a price worth paying.

What effect will the Conservative-DUP deal have?  The DUP is known to be very pro-Israel, and when Board of Deputies colleagues met DUP leader and Northern Ireland First Minister Arlene Foster last year, she expressed her full support for our Jewish Manifesto. The party has had a proud record of standing up for the Belfast Jewish Community when it has come under attack. The DUP's socially conservative views on LGBT issues and abortion are of concern to large sections of our community, but early indications are that these will not form any part of a confidence and supply deal with the Conservative Party. 

As for Labour, it clearly has a lot of work to do if it is to overturn the suspicions of Jews in these seats that Labour might have to win to form a government. Jeremy Corbyn has said that the party needs to "stand up, not stand by", when it comes to prejudice, and the party must take much firmer and more decisive action against the antisemites in its midst.

Jeremy Corbyn himself has to make a clear break from treating extremists as "friends" and start standing up consistently for their victims instead. This has to apply everywhere, including of course the UK and Israel. The party needs to guarantee that it will not apply a policy of boycotts, divestment and sanctions to Israel, and the party should ensure that it is not a cold house to Israel, and gives the country the credit it deserves for its many achievements.

The Jewish vote is pivotal in certain key seats. Whether the next election is in three months, one year or five years, the parties should realise that they have much to gain from listening to our community.

Gillian Merron is chief executive of the Board of Deputies