Brits have “been pushed to breaking point” by the longest squeeze on wages in modern history, the TUC general secretary has warned.
In her final congress speech, Frances O'Grady will blast the "toxic" Tories for their botched handling of the economy and say families "cannot afford to tighten their belts any more".
Analysis for the union body puts workers on course for a £4,000 real wage drop over the next three years, due to inflation outstripping growth.
Workers won't see their pay hit 2008 levels in real terms until 2028, the TUC said.
Addressing the TUC's annual conference in Brighton on Tuesday, Ms O'Grady will say: "We need an economy that rewards work - not wealth.
“But under the Conservatives working people have got poorer, while shareholders have got richer.
“We’re in the longest squeeze on real wages since Napoleonic times. The worst in modern history.
“And if ministers and employers keep hammering pay packets at the same rate, UK workers are on course to suffer two decades – twenty years - of lost living standards."
She will demand ministers "stop the rot", adding: "Families cannot afford to tighten their belts anymore - they are at breaking point."
The outgoing TUC boss will also warn the Government "we'll see you in court" if they press ahead anti-strike legislation.
Liz Truss pledged to bring forward legislation in her first 30 days in No10 to introduce minimum service levels during strikes by transport workers but her plans were derailed by the crisis caused by her own mini-Budget
"It's a cynical effort to distract from the mess this Government has caused," she said.
"If ministers cross the road to pick a fight with us then we will meet them halfway.
"Today I give ministers notice. We've already taken legal counsel and we know you're in breach of international law and trade deals that enshrine labour standards.
"So read my lips: we will see you in court."
Union chiefs are threatening a winter of discontent, with hundreds of thousands of workers due to be balloted for strike action over pay.
Several motions will be put forward at congress to ask the TUC to coordinate walkouts for maximum impact with ballots held in sectors from the NHS to rail.
A Government spokesperson said: “The Government is determined to make work pay and in April we increased the National Living Wage to £9.50, the largest ever increase since its introduction in 2016.
“We know the pressures people are facing with rising costs, which is why we are supporting people with their bills including vulnerable households receiving £1,200 in direct payments, on top of the Energy Price Guarantee.
“In the long-term, we are committed to building a high skilled, high wage economy that delivers on our ambition to make the UK the best place in the world to work.”
