The UK is on course for two decades of “lost living standards”, a union leader is warning.

TUC general secretary Frances O’Grady said workers were being “pushed to breaking point” amid the ongoing cost-of-living crisis.

In her final address to the TUC Congress as head of the union federation before stepping down, she will call for an economy “that rewards work – not wealth.”

We’re in the longest squeeze on real wages since Napoleonic times. The worst in modern history

She will tell delegates at the opening of the conference in Brighton on Tuesday: “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.

“If ministers and employers keep hammering pay packets at the same rate, UK workers are on course to suffer two decades of lost living standards.

“Over the next three years alone real earnings are set to fall by another £4,000.

“We have got to stop the rot. Families cannot afford to tighten their belts anymore – they are at breaking point.”

Downing Street says we need to focus on growth, not wealth redistribution. Well, they have no plan for growth, but they do have one for redistribution. They are lifting the cap on bankers’ bonuses and driving down public servants’ pay

She will also repeat her criticism of government plans on industrial action, which the TUC has already pledged to fight in the courts.

“Just when the citizens of this country are in despair, when key workers’ kids are going to school with holes in their shoes, and young families are worried sick about taking on a mortgage – Liz Truss’s top priority is to make it harder for workers to win better pay.

“It’s a cynical effort to distract from the mess this Government has caused.

“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.”

She will say that the Government cannot be trusted with the economy, describing the Conservatives as “toxic.”

She will add: “We know who creates real wealth in this country.

“It’s not hedge fund managers who made a mint by betting on the pound crashing. Or the former chancellor who popped champagne corks with them afterwards.

“It’s the honest, hard-working people of this country.

“Downing Street says we need to focus on growth, not wealth redistribution.

“Well, they have no plan for growth, but they do have one for redistribution. They are lifting the cap on bankers’ bonuses and driving down public servants’ pay.”

The TUC estimates that real wages will not recover their 2008 level until 2028.

This will result in workers losing a further £4,000, on average, over the next three years as a result of inflation outstripping wage growth, it estimated.