On Monday night, after a long period in which Labour appeared to be drifting towards backing some form of membership of the single market, Jeremy Corbyn appeared to rule it out. During a meeting of the Parliamentary Labour Party, Corbyn rejected a proposal from the SNP for a united opposition summit to support membership. Corbyn’s choice of words in describing what Labour will support, “the full benefits of the single market”, is consistent with the party’s earlier position, but means voters largely remain in the dark over the exact type of Brexit the party would look to deliver in the future.

A variety of arguments have been used by senior Labour figures to back up Corbyn’s remarks. Perhaps most tellingly, a senior party source told the Guardian that “the single market is not a membership club that can be joined so we seek through negotiation to retain the benefits of the single market.” This assertion may sound authoritative, but it doesn’t stand up to scrutiny. Non-EU members of the European Economic Area (EEA), like Norway and Iceland, are part of an organisation which has members and a set of rules and benefits. While full membership of the single market does mean EU membership, this second tier form of membership, the EEA, covers a more limited range of areas. In any ordinary meaning of the term used in my field, International Relations, however, the EEA is a membership club.

For states looking to interact with the single market, negotiation is the means, and membership (or non-membership) the outcome. What distinguishes the notion of a single market from a more limited trade agreement is the commitment its members make to be bound together by shared rules and regulations agreed at the European level. Because the unity of these rules gives the market its single character, individual members cannot cherry pick the ones they like or dislike.

The rhetorical distinction that Corbyn makes between negotiation and membership is a strange one, and in reality probably stems much more from the need for Labour not to commit to any particular Brexit outcome than it does from a concerted attempt to take a policy stance.

Fundamentally, Labour is still fudging the issue – although we can look at how this fudge might translate into policy if left unresolved.

Labour are hinting at something similar to the Switzerland model – a series of bilateral treaties, rather than membership of the EEA. But although Switzerland’s bilateral treaties are nominally individual, they also include a “guillotine clause”, under which a breach of one treaty nullifies all of them. And so Switzerland is, in effect, a member of the single market.

When a referendum voted narrowly to end free movement in 2014, the Swiss were not able to negotiate this with the EU without losing their participation in the single market – because ending free movement would have cancelled all of Switzerland’s other agreements with the EU.

For the Swiss, as for Labour, this involves a set of political rather than practical decisions. The Swiss public rejected single market membership by referendum in 1992, and, while the Brexit referendum was in no way a mandate to leave the single market, Labour is hesitant to tackle that debate head on.

But Labour can only fudge the issue for so long. In October, parliament will be presented with a deal negotiated by Theresa May, and if Labour wants to oppose it they will have to provide a more detailed explanation of what their alternative might look like.

In truth, a confident Labour Party, which has now been consistently ahead of the Tories in the polls for seven months, should have the courage to put forward a bold vision. Like the rest of Corbyn’s platform, Labour’s Brexit policy should stem from principles, not just electoral calculation. Labour could tackle the narrative that immigrants are to blame for falling living standards, keeping free movement with enhanced social and workplace rights. Remaining in the single market would achieve this – and would retain many of the progressive elements of EU membership such as workers’ rights, environmental protections, human rights, and initiatives like Erasmus.

Perhaps the newly rejuvenated Labour Party could afford to be bolder still. While non-EU members of the single market are consulted on rule changes that affect them, ultimately they are rule takers and not rule makers. While these arrangements work, they would put limits on how a socialist government with an international vision could transform the wider European political scene.

Just think how Labour in power could shift European politics to the left, and with it some of the EU’s own policies and thinking. But while leaving the single market could well be a disaster for the “jobs first” approach that Labour proposes, merely staying in it would leave a Corbyn government unable to meaningfully influence the EU and its member states.

Corbyn’s Labour is changing British politics, promising a route to a new economy and a politics of hope for millions of disenfranchised people. Theresa May’s Brexit deal will bring a future of yet more disenfranchisement and poverty, and will have no popular mandate.

When it returns to parliament, MPs should have the courage to let the British people decide their future with a fresh referendum on the terms of the deal. And at that point, as Corbyn has already acknowledged, the best option ought to be clear: to remain in the EU.

Luke Cooper is senior lecturer in politics at Anglia Ruskin University and the Convenor of the Another Europe Is Possible campaign.