As most party members know all too well, Labour will face its first major electoral test under Jeremy Corbyn this May. Crucial as these polls are for all of us, particularly our candidates, we cannot blithely assume that they will be the only contest that we will face this year. We need to be on a general election war footing.

In June, decades of Tory infighting are set to reach a crescendo with the referendum on membership of the European Union. The prospect of the Prime Minister standing down in the event of a vote to leave has been often mooted. However, I believe that the forces unleashed within the Conservative party are so great that, whether Cameron wins or loses, many of their MPs and activists will feel it is time for a change at the top. Cameron fired the starting gun on the race to succeed him when he announced that he will not fight another general election and, as Tony Blair can testify, once the lid is off the bottle it can be very difficult to re-seal it.

In the event that Cameron goes, I expect his successor to look very keenly at whether the Labour party is capable of fighting a snap general election. The new Conservative leader would, of course, insist this was nothing to do with naked political calculation. You can already imagine the argument, a new Tory leader arguing that “unlike Gordon Brown, I am not going to be an unelected Prime Minister”.

Many people assume that the Fixed Term Parliament Act would prevent the Tories from cutting and running but they are wrong. The Act, designed to hold the coalition together, does allow an early general election to be called if agreed by two thirds of the House of Commons. If a new Conservative leader demanded a general election it is impossible to imagine how Labour could refuse to go to the country.

I know that Labour members have welcomed the sense over recent weeks that the parliamentary party has started focusing more attention on the upcoming elections than internal squabbling. However, we cannot afford to be complacent about the scale of the challenges facing us nor the urgency of resolving them.

The chasm between current political perceptions of the party and the position we would need to be in to win a general election plus the work that is still required in terms of policy development, fundraising, organisation, candidate selection and more. If Labour is confronted with a general election whilst intellectually and organisationally under-prepared, divided and under-resourced we would be hurtling towards catastrophe. The Liberal Democrats stand as a warning to all political parties about the scale of devastation that can befall parties in the modern era where tribal loyalties offer much less protection from the vagaries of political opinion that they did during elections of the past. The Lib Dems inability to make any headway shows that numbers matter, no two defeats are the same.

More than any government in history, these Tories have attempted to use the power of government to tactically weaken us, their main opponent. Tory moves on trade union funding, voter registration, boundary changes and political party funding all demonstrated that there are no tricks too low for them to consider if it will weaken our party and our movement. They are not attempting to beat Labour in one election but to destroy our capacity to oppose them for good.

So, this spring, MPs and party members will rightly be out campaigning in support of our councillors, mayoral candidates and police crime commissioners in England; our MSPs in Scotland; and AMs in Wales, because these elections are important in their own right. But we should remember that they could be a dress rehearsal for the biggest fight of all and prepare accordingly.

Being match fit for a general election campaign poses financial and organisational challenges of course, but it also means articulating a cohesive and settled vision of what Jeremy Corbyn’s Britain would look like.

So, the fight for the future of the Labour Party is not a theoretical internal discussion point, but a stark and real description of the existential battle that may be upon us much sooner than some expected. We haven’t got a moment to lose.

Toby Perkins is MP for Chesterfield and a Shadow Defence minister