Dozens of Labour councillors have written to Keir Starmer begging him to offer voters a chance to change their minds on Brexit.
Nearly 70 have added their names to the letter, which urges the shadow Brexit secretary to help shift the party’s position “in the national interest”.
The councillors, all from south London, say the economic outlook is “bleak” in the boroughs they represent.
Their letter, which criticises the “weakest prime minister in living memory”, states: “Instead of generating extra money for the NHS, Brexit is costing the country billions. Instead of bringing about pay increases for British workers, Brexit has made it harder for struggling families to make ends meet. Instead of easing pressure on public services, Brexit has exacerbated a shortage of nurses to staff our hospitals. Instead of uniting the country behind a new national mission, Brexit has raised the likelihood of the breakup of the United Kingdom.
“Needless to say, these issues affect people who voted for Leave every bit as much as those who voted for Remain.
“EU citizens report increased levels of anxiety and depression, brought on by the shameful delay in securing their rights.
“British residents with families abroad are also facing additional burdens and stresses. Local NHS institutions struggle to fill vacant posts, just as the onset of winter increases demand for their services.
“Businesses tell us of their frustration at the continued uncertainty around the economic direction of travel; some have postponed expansion plans, others are making contingencies to relocate staff overseas.”
Many Labour politicians and campaigners believe the party should be campaigning for the UK to remain a part of the single market and customs union after it leaves the EU in March 2019.
Starmer wants to negotiate an “early agreement for strong transitional arrangements” on the same terms the country currently enjoys - which would mean a time-limited period where Britain would remain within both, accepting their common rules and retaining the jurisdiction of the European Court of Justice.
Labour’s leadership is expected to come under increasing pressure to strengthen its Brexit position in the coming months, with union bosses reportedly lobbying Jeremy Corbyn’s team behind the scenes.
The letter from councillors does not call explicitly for a second referendum - but does not rule it out - calling for the electorate to be given “the opportunity to say whether leaving the EU is really in the best interests of the country”.
It adds: “The mechanism by which voters have their say must be an open question, but Labour should be clear that the electorate’s role in this process did not end on 23 June 2016.
“On the biggest issue facing our country since the Second World War, Labour should be committed to providing the opportunity for people to change their mind.
“Doing so would demonstrate bravery, maturity and the principled leadership the country so desperately needs. It would kill off the notion that there is space in British politics for a new party to emerge.
“And it would reinforce voters’ growing recognition that Labour is a government in waiting, ready to serve the many, not the few.”
Southwark councillor James Coldwell, one of the leading signatories, said the decision to make the letter public had been made in a bid to get more councillors’ voices heard in the Brexit debate and encourage other elected and party members to speak out.
It goes on: “We hope you receive the letter in the spirit of fraternity with which it is sent, and would welcome the opportunity to discuss these ideas with you further.”