The government is almost half way through the negotiation of the UK’s withdrawal from the European Union. At this moment in our history, when the country needs leadership and a vision of the future, the Tory government provides neither. As Jeremy Corbyn said this week, with a prime minister held to ransom by the hard right of her party and unable to provide any direction, “they are on the road to nowhere,” because they cannot agree on our future relationship with the EU.

In the absence of any leadership from the government, our party has a historic opportunity and a duty to set out a clear direction for our country. Working in the national interest with elected representatives from other parties, our party can help marshal a majority for a different course which ends austerity, promotes equality, social justice and environmental sustainability.

Working through the EU customs union we have no tariffs on goods traded with our closest neighbours, we apply the same tariffs to goods from outside the EU and we have the benefit of over 60 trade deals around the world. As TUC general secretary Francis O’Grady said earlier this month, by ruling out the UK continuing to participate in the EU’s customs union the Tory government is choosing to put up barriers to UK trade with Europe after Brexit which will be “bad for jobs, bad for investment and bad for business”. That is why it is right that Labour seeks to take all necessary steps to ensure the UK permanently participates in a customs union on the same terms as we do now, as shadow cabinet members have already said we will do.

But our commitment to social justice dictates that we should also seek to participate in – not simply have “access” to – the EU’s single market. Why? Because the single market is more than a free trade zone between EU countries. It is a framework of rules – including on employment rights, consumer and environmental standards – that protects people from the worst excesses of globalisation and unfettered capitalism. As set out in the recent Labour Campaign for the Single Market/Open Britain pamphlet, “Busting the Lexit Myths”, it is no capitalist club, which is precisely why the single market is hated by the Tory right; nor does it stand in the way of us delivering on our manifesto promises.

Indeed, if we want to be able to fund our anti-austerity investment programme we can’t afford the multibillion pound hit to the public finances that leaving the single market would entail. We can only properly fund local services, schools, hospitals, social care and international development if our businesses thrive and our economy grows. And, if we want to build a modern, low-carbon economy that protects workers and tackles tax avoidance, we will only achieve it through collaboration and frictionless trade with our nearest neighbours.

So – as a minimum – Labour must clearly and unambiguously set as a negotiating objective the goal of remaining part of the European Economic Area, in order to participate on a permanent basis in the single market. Other non-EU countries are in the European Economic Area, the EU has said this option is available to us and it is the only way we can continue to enjoy the exact same economic benefits of our existing arrangements if Brexit happens. Theresa May has ruled this out – the vast majority of those who voted for us last year did so in the belief that we would do all we can to oppose this.

Above all, the prospect of a hard border between Northern Ireland and the Republic of Ireland poses a threat to the Good Friday Agreement. Helping to bring it about was one of our party’s greatest achievements. Colum Eastwood, the leader of our sister party the SDLP, said this week that “the people of Northern Ireland want – but also need – the UK to stay in both the single market and customs union to protect us from a hard border”. He put it well when he said “we shouldn’t play games with the peace process or with our economy”, leaving no room for fudge or ambiguity. This is a view reiterated by the Irish government.

Given the parliamentary arithmetic and the numbers of parliamentarians from other parties – including Conservative backbenchers – who have indicated they will join us in this endeavour, our country’s continued participation in a customs union and the single market is now in the Labour Party’s hands. For the sake of building a better Britain and safeguarding those our party was founded to protect, we must grab this chance before it is too late. We will never be forgiven if we fail to do so.

Heidi Alexander MP, co-chair Labour Campaign for the Single Market; Alison McGovern MP, co-chair Labour Campaign for the Single Market; Chuka Umunna MP, former shadow business secretary; Lord Neil Kinnock, former leader the Labour Party; Rushanara Ali MP; Ben Bradshaw MP; Paul Brannen MEP; Chris Bryant MP, former shadow leader of the house; Ruth Cadbury MP; Lord Michael Cashman; Stella Creasy MP; Seb Dance MEP, deputy leader, European Parliamentary Labour Party; Stephen Doughty MP; Julie Elliott MP; Lord George Foulkes; Kate Green MP, former shadow equalities minister; Theresa Griffin MEP; Baroness Doreen Lawrence; Baroness Margaret Jay; Darren Jones MP; Baroness Helena Kennedy QC, human rights lawyer; Liz Kendall MP; Wajid Khan MEP; Peter Kyle MP; Stephen Kinnock MP; Jude Kirton-Darling MEP; Chris Leslie MP, former shadow chancellor; Seema Malhotra MP, former shadow chief secretary to the treasury; Lord Peter Mandelson; David Martin MEP; Alex Mayer MEP; Baroness Sally Morgan; Councillor Warren Morgan, leader, Brighton & Hove city council; Clare Moody MEP; Madeleine Moon MP; Lord Bill Morris, former Unite general secretary; Ian Murray MP, former shadow Scottish secretary; Councillor Lib Peck, leader, Lambeth council; Bridget Philipson MP; Lord Jeff Rooker; Baroness Jan Royall, former shadow leader of the House of Lords; Angela Smith MP; Catherine Stihler MEP; Wes Streeting MP; Councillor Huw Thomas, leader, Cardiff city council; Derek Vaughn MEP; Julie Ward MEP; Martin Whitfield MP; Dr Paul Williams MP; John Woodcock MP; Councillor Clare Coghill, leader, Waltham Forest council; Sir Steve Bullock, mayor of Lewisham; Councillor Peter John OBE, leader, Southwark council; Councillor Steven Cowan, leader, Hammersmith & Fulham council; Councillor Cammy Day, Labour group leader, Edinburgh city council; Joe Anderson, mayor, Liverpool city council; Councillor Nick Forbes, leader, Newcastle city council; Councillor Frank McAveety, Labour group leader, Glasgow city council; Lynne Neagle AM, national assembly for Wales; Vikki Howells AM, national assembly for Wales; Jane Hutt AM, national assembly for Wales; Pat McFadden MP; Meg Hillier MP, chair, public accounts committee; Daniel Zeichner MP; Kerry McCarthy MP, former shadow environment secretary; Mary Honeyball MEP; Conor McGinn MP; Virendra Sharma MP; Margaret Hodge MP; Lord Andrew Adonis; Gareth Thomas MP; Councillor Huw Thomas, leader, Cardiff city council; Councillor Debbie Wilcox, leader, Newport city council; Councillor David Poole, leader, Caerphilly county borough council; Councillor Anthony Taylor, deputy leader, Neath Port Talbot county borough council; Councillor Simon Pritchard, leader, Pontypridd town council; Lord David Triesman, former Labour Party general secretary; Lord Tony Young, former CWU general secretary; Lord Clive Hollick; Stephen Timms MP; Gavin Shuker MP; Mary Creagh MP, chair, environmental audit committee and former shadow secretary of state for international development; Luciana Berger MP; Florence Nosegbe AM, Greater London assembly; David Rees AM, national assembly for Wales; Joyce Watson AM, national assembly for Wales; Mike Hedges AM, national assembly for Wales; Dawn Bowden AM, national assembly for Wales.