Nearly 50,000 people have signed a petition backing former prime minister Gordon Brown's call for an emergency budget to tackle the cost-of-living crisis.
On Monday Mr Brown warned people will have to go without food and will be unable to heat their homes by October if the government does not take urgent action.
He told Sky News he was seeing poverty in his hometown in Fife "that I did not expect to see ever again in my lifetime" and branded the Conservatives' windfall tax as "stupid", claiming the opt-outs included in the tax brought forward when Rishi Sunak was chancellor reduced the value from £15bn to £5bn.
The former prime minister has been joined by metro mayors, anti-poverty groups and faith leaders in demanding urgent government action on Universal credit and support for families.
The petition says: "The government raised Universal Credit during the pandemic - providing a lifeline to millions - and with enough pressure, they could do it again."
Mr Brown said: "People are being asked to bear an unbearable burden of unpayable bills at a time when so many are under pressure."
Campaign group 38 Degrees said within 24 hours of going live tens of thousands of people had signed the petition.
Ellie Gellard, strategic director at 38 Degrees, said: "The stories we're hearing from people all over the country could come straight out of a Charles Dickens novel: kids going hungry, mums who are sick yet working three jobs to make ends meet, families facing freezing in their own homes.
"Now, with news that energy bills could ramp up to £4,000 next year, the panic felt by millions is only going to get worse.
"All while our government is out of office on their summer holidays and the candidates vying to be our next PM are silent. For families on the edge, that silence is deafening.
"In a matter of hours, tens of thousands of members of the British public have backed Gordon Brown's calls for an emergency budget - and a plan to bring down crippling bills and support families, immediately."
A campaign spokesperson for prospective prime minister Liz Truss said: "Rishi Sunak wouldn't know how people benefit from a tax cut because he has never cut a tax in his life. People didn't vote for the Conservative Party to be subjected to old fashioned Gordon Brown style politics of envy.
"You cannot tax your way to growth and Liz's agenda is to build a high wage, high growth, low tax economy that supports people. Liz believes in people keeping more of their own money, not Rishi's socialist tax and spend which will lead us to recession."
Responding to Ms Truss saying she will now look at providing direct support payments, a spokesperson for Rishi Sunak's campaign said: "This is a major u-turn on the biggest issue currently facing the country.
"It's all very well offering empty words about 'doing all you can'. But there aren't lots of different ways to act on this. Taking action means providing direct support, which Truss had previously dismissed as 'handouts'.
"Twice now, Truss has made a serious moral and political misjudgement on a policy affecting millions of people, after last week reversing plans to cut the pay of teachers and the armed forces outside London. Mistakes like this in government would cost the Conservative Party the next General Election."