Parliament’s approach to the draft European Union withdrawal agreement can either reaffirm or undermine public trust. Observing the manoeuvring around it, I despair at the insincerity of some. The UK held a referendum in 2016 with huge participation; and a subsequent general election at which Labour and the Conservatives promised to respect the outcome. My pledges in 2017 included: “When Britain leaves, I will work for a deal that works for Doncaster … I don’t support a second referendum. We need to bring people together, whether they voted Leave or Remain.”

Labour voted to trigger article 50 – beginning our formal withdrawal. Labour backed a transition period – to enable detailed trade and security matters to be negotiated. Labour has not supported single-market membership. Labour recognised that free movement would end and supported a permanent customs union arrangement – allowing the UK to strike its own trade deals not membership of the existing EU customs union. I have backed all of these positions advanced by Labour’s frontbench. Some Labour colleagues have not, their intention throughout being to overturn the 2016 vote.

A sad coalition of extremes is coalescing to stop any deal: hard Brexiters, for whom compromise with the hated EU must be thwarted; fuelled by the knowledge that if no agreement commands a majority a no-deal Brexit becomes the default outcome; and ardent remainers who warned of the dangers of a cliff-edge Brexit, now hoping to defeat a deal and force a crisis to secure a second referendum. Polar opposites are united: Boris Johnson and Tony Blair condemned the deal before reading a word of the 585 pages.

In 2016 a Labour MP told the Evening Standard: “I really have no time for calls for a second referendum because I think it comes across as disrespectful to those who voted to leave.” He added in the same interview that Blair’s government had lost trust by underplaying the numbers who would come from the EU accession countries. “That one mistake ... may I think have been the biggest driver of why we left the European Union.” He was correct on both counts. Except the MP Chuka Umunna now campaigns to overturn the referendum result.

Some Labour MPs pretend that defeating May’s agreement will lead to an election. It won’t. They don’t even believe it.

Apparently, 250 “People’s Vote” volunteers hope to persuade my constituents they were wrong to vote Leave. In 2016 I would have welcomed even two dozen as I slogged the streets for remain, finding little love for the EU. Some MPs – Lisa Nandy, Gloria De Piero and Gareth Snell among them – show real empathy for small-town Britain. For many lifelong Labour voters, who happened to vote Leave; voters told in so many ways that they are stupid or worse. My leave-voting Don Valley constituency is made up of more than 30 small towns, mining communities and villages: worlds away from our metropolitan and university cities. Six out of 10 Labour MPs represent seats such as mine.

The most frequent comments from voters now are: “Caroline, why haven’t we left yet?” And “Can’t you work together to sort this out?” I have been honest with remain voters about honouring the 2016 result, and my general election pledges. Equally, I have insisted to leave voters that a deal is the best outcome for jobs. Jeremy Corbyn is right when he argues we must bring leave and remain voters together. That’s why I called on the government to adopt a cross-party approach and invite Labour into their negotiating team. The government can never please the Tory hardline European Research Group faction. It’s not too late for the government to reach out to Jeremy Corbyn on aspects of an agreement. I have no idea what is going to happen next. The Government is imploding. While chaos reigns, few are focusing on the details. MPs promote agendas that have little to do with the agreement. Debate remains polarised.

But if parliament rejects Theresa May’s deal, I want assurances from my frontbench that we won’t become the accomplices of the hard Brexiters, leaving the UK crashing out on 29 March. On this crucial question, I have a right to know how we guarantee toavoid the worst of all outcomes.

I too want a Labour government and if Jeremy Corbyn tabled a no-confidence motion I’d back it. Since the Fixed-term Parliament Act, not one motion of no confidence has been tabled in six years. Some Labour MPs pretend that defeating May’s deal will lead to an election. It won’t. They don’t even believe it, yet raise false expectations among Labour supporters. This moment calls for honesty, not posturing. If after all the bluster, confusion, and parliamentary procedures, the Commons reaches a stage where MPs are left with no more options on the table – just one agreement or leaving with no deal – I know where my duty lies. Not to help May, not to help the government, but to do what I believe is in the best interests of my constituents and the country.

Parliament has endlessly debated Brexit. I wish Britain’s towns and coastal communities had received the attention in that time they deserved. The advance of working people has been due to Labour Governments, not the EU. Labour introduced paid holidays and a minimum wage in the UK; not Brussels. Labour must develop a post-Brexit agenda with a vision for their future, not a repeat of the referendum.

• Caroline Flint is the Labour MP for Don Valley