Now that the article 50 notification bill has passed in the House of Commons, the debate moves on from how we should have voted, to what deal the government is going to secure in the forthcoming negotiations.

Labour has said it will press for the “best possible deal” and will continue to harass the government on this. But, as things stand, we won’t have much influence over ministers, as illustrated by the fact we lost all the votes on the amendments tabled to the bill.

The big question is: what do we do if the government takes us in an unacceptable direction, towards a bad, costly and economically damaging deal that threatens jobs and undermines rights?

Labour will not be able to credibly vote for Theresa May’s Brexit in just under two years time if her deal leaves our manufacturers facing barriers to our main export market, hinders our universities and researchers from participating in European collaboration, fails to guarantee workers’ rights and environmental protections, prevents our hospitals from accessing radioactive isotopes for cancer treatment, ends the ability of our financial sector to operate across Europe, severely damages our public finances, or leaves Britain dependent on the goodwill of Donald Trump.

We would then have to oppose the article 50 “divorce” deal when it comes before Parliament. We cannot afford to be complicit in a disaster.

Indeed, some already see us that way. Labour has lost members and voters – and to the Lib Dems and Greens, rather than, as some had feared, to UKIP.

Those MPs in constituencies which voted to leave have been wary of appearing to take a different view from their voters, but are finding that shifting to a pro-Brexit position loses support from among the majority of Labour voters who voted Remain, while often undermining their credibility. And not all Leave voters put this issue above every other one.

By the time the article 50 divorce deal comes back, the Tory government will have been in power for nine years and May’s honeymoon period will be well behind her. The deep divide over Europe at the heart of the Tory party, remarkably well disguised in the past few months, may well open up again. Combine a significant split in the Tory party, and strong opposition from Labour, and we could actually defeat the government on the deal.

In terms of domestic politics, that would put them on the back foot. In terms of the EU, rejecting the deal can mean one of two things: negotiate further or reconsider Brexit. Article 50 notifications can be withdrawn, contrary to what the government has claimed.

Much will depend on the state of public opinion by then. It is striking that polls show that the public has not rallied behind Brexit following the referendum, as one might have expected, and certainly not behind the government’s hard Brexit.

Few Leave voters support Brexit-at-any-cost and they do not want a bad deal for Britain. As the costs of Brexit become clearer, many of them will be angry about the lies told them on a big red bus.

Richard Corbett is MEP for Yorkshire and Humber and deputy leader of the Labour group in the European Parliament.