MPs have suggested that a “north-south divide” in the Conservative party could be its “undoing” and lead to a string of rebellions against Boris Johnson unless he commits to moving northern cities and regions out of the harsh coronavirus lockdown. Fifty-five MPs representing northern regions of Britain signed a letter calling for a focus on “levelling up” the regions and a roadmap out of Covid-19 restrictions, saying it was a warning shot to show they had the numbers to inflict a government defeat. Government sources said there was no plan to set out specifics on how curbs could be lifted for areas under tier 2 or 3 restrictions, stressing that the emphasis was still on persuading people to follow the rules as cases and hospitalisations remained high. The Conservatives’ prized red-wall seats, many won for the first time from Labour in 2019, have borne some of the worst effects of Covid-19, in illness and economic terms. On Tuesday more than half of the 207 Covid-19 deaths announced by NHS England were in the north of England, and the region was reported to have more than half of all patients on ventilation beds. The MPs, in the Northern Research Group, led by Jake Berry, former minister for the northern powerhouse, wrote to the prime minister demanding a “clear roadmap” out of lockdown and arguing that the Covid pandemic had “exposed in sharp relief the deep structural and systemic disadvantage faced by our communities”. “This north-south divide in the Tory party could be our undoing,” one southern Tory MP said. “These are MPs who delivered our victory, but far from a spending splurge in their towns they’ve seen their constituents placed under lock and key for months while the south gets more freedoms. “Unless the chancellor opens his cheque book to signal a spending-led recovery these MPs are going to get very agitated indeed and they have the numbers. But then seats like mine are going to pay for it in tax rises.” The show of strength in the numbers – enough to defeat Boris Johnson’s majority – was an important part of the group going public, one MP said. “You sometimes have pressure groups that don’t want their guns to be counted. But on this occasion it gives an indication of the strength of the group as a whole. It doesn’t do any harm for governments to know that there’s a group of MPs who are paying particular attention to particular issues and will vote accordingly, in the interests of constituents.” However, some in the group said they did not realise the intention had been to go public with their concerns and said they had hoped to be able to make private representations to Johnson, stressing that the act of sending the letter was not “hostile”. Pressure is likely to be applied over any new coronavirus restrictions and on the chancellor, Rishi Sunak, when he publishes his one-year spending plan in November. The one-year plan, which replaces the comprehensive spending review, delayed for a second time, is intended to be concerned entirely with the pandemic response. But MPs said there had to be a “signal of intent” about the levelling-up agenda beyond the virus. Sunak, the MP for Richmond, North Yorkshire, moved to ease concerns on Tuesday, saying the government was committed to infrastructure, skills and broadband spending. “I absolutely share my colleagues’ frustration at restrictions. Of course that’s frustrating if you’re having to live under these things, and you want to know when it’s going to be over,” he said, without committing to any further steps. MPs who signed the letter said they wanted to see concrete action, on lockdowns and with regard to a wider agenda. David Jones, the former Brexit minister, who signed the letter, said: “The seats of northern Britain delivered the government’s majority. So what we’re looking for is an expression of commitment or a reassertion of the government’s commitment that they understand the need to level up the north and bring more equality to the country as a whole.” Simon Fell, Conservative MP for Barrow and Furness, said the group was “trying to essentially keep the government honest on its promises to the north”. Among his demands Berry has urged the government to publish information in an “easily digestible, consumer-facing, public-friendly way” akin to how church halls use large mock thermometers to display progress with fundraising.