More than 50 Tory MPs have written to the prime minister calling for a "clear road map" out of lockdown restrictions in northern England, warning the region risks being "left behind".
The letter from the Northern Research Group said the pandemic threatened Boris Johnson's pledge to "level-up".
They also called for an economic recovery plan for the region, arguing it had been hardest hit by the virus.
No 10 said it was "committed to levelling up across the country".
And speaking to BBC Newsbeat, Chancellor Rishi Sunak said that he shared the MPs' "frustrations at restrictions" adding that the government wanted to invest in northern areas.
All the areas under the strictest restrictions of the government's three-tier system for England are in the North or the Midlands.
Warrington has become the latest area to join the Liverpool City Region, Greater Manchester, Lancashire and South Yorkshire in the top tier, while Nottingham and parts of the surrounding county will move into the highest tier on Thursday.
This will mean about eight million people in England will be living under the toughest restrictions, which are reviewed after 28 days, by the end of the week.
In areas under tier three rules, pubs and bars not serving substantial meals must close and households are not allowed to mix indoors or outdoors in hospitality venues or private gardens.
Russ Bowden, Labour leader of Warrington Council, said he could not see a way out of the top tier of restrictions for his area, adding that he did not know what measurements the government were using for putting places in tier three in the first place.
He also told Radio 4's Today programme: "There are no clear rules about what the success criteria are with the tiers and how you move between the different tiered layers."
Labour leader Sir Keir Starmer has previously raised the issue in the House of Commons, saying that the top tier was a "gateway" to potentially months and months of "agony" from which there was no exit.
Prime Minister Boris Johnson said that the "simplest and most effective way" for areas to get out of tier three was to get the R number - the rate at which the virus is spreading - "down to one or below".
The Department of Health also said other data taken into account included which age groups were being affected and the pressures facing the NHS in those areas.
Virus 'increasing disparity'
Some 40 Conservative MPs representing areas in the north of England, North Wales and the Scottish borders, have publicly signed the letter, including former cabinet ministers David Davis, David Mundell and Esther McVey, while a further 14 have had their names redacted.
The newly-formed Northern Research Group of Tory backbenchers is led by former Northern Powerhouse minister Jake Berry.
In their letter, the group called for the prime minister to set out "a clear road map down the tiering system and out of lockdown", warning restrictions were "disproportionately" affecting people in the north of the country.
"The virus has exposed in sharp relief the deep structural and systemic disadvantage faced by our communities and it threatens to continue to increase the disparity between the North and South still further," they said.
Mr Berry who represents Rossendale and Darwen said "We are asking people to give up huge civil liberties, businesses to close, people to live on two thirds of their normal wages.
"I don't think it is unreasonable to say the other side of that coin should be 'show us the way out'."
He also denied that he and other northern MPs were staging a "revolt" against the government, saying they were asking the prime minister to "reaffirm" his commitment to "stimulate the North".
December's general election saw the Conservatives demolish the "red wall" - winning seats in the north of England from Labour it hadn't held in a generation.
The government pledged to repay that support before the pandemic hit, throwing normal politics up in the air.
Boris Johnson has continued to talk about that agenda - but the signatories of this letter are worried that Covid will see some of the pledges made fall down the political priority list.
In particular, they share concerns with many Labour leaders in the North that there isn't a clear road map out of restrictions.
It's been a bruising few weeks for the government's relationship with the North, with very public rows over support for local economies.
These MPs support the government - and say their intervention is designed to influence its plans. But it also shows fears for the north of England are shared across the political spectrum
The group welcomed the financial support already in place for businesses, such as the furlough scheme and extra funding for local authorities under the tightest coronavirus restrictions.
But they added: "We do however share concerns that the cost of Covid could be paid for by the downgrading of the levelling-up agenda, and northern constituencies like ours will be left behind."
Mr Johnson won a majority of 80 seats in December's election, with many traditionally Labour constituencies in the so-called "Red Wall" turning Conservative blue.
A key part of his campaign was a pledge to "level-up" and reduce regional inequality across the country.
Mr Sunak said he understood the MPs' concerns but added: "I also share their passion and their ambition for the North" and promised that the government "remained committed" to investing in these areas.
Shadow Treasury minister Bridget Phillipson said the government had been "treating local communities with contempt".
She added that the decision not to extend free school meals over the half-term holiday "is the clearest sign yet that the Conservatives have the wrong priorities and are not on the side of British families".
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