The Government is to be told that its "brutal" spending cuts are hitting jobs, services and living standards amid calls from union leaders for a general strike.
Ministers will come under attack as tens of thousands of workers, anti-war campaigners, politicians, community groups and other activists join a huge protest rally in London. More than 250 coaches have been booked to bring people to London, while similar protests will also be held in Belfast and Glasgow.
Labour leader Ed Miliband will be among dozens of speakers at a rally in Hyde Park, joining union officials who will spell out the impact of spending cuts on public services.
There have been growing calls for the TUC to organise a general strike following last year's day of industrial action by public sector workers over the Government's controversial pension reforms. The events are aimed at calling on the coalition to end its public sector spending cuts and other unpopular policies.
TUC general secretary Brendan Barber will tell the rally that austerity wasn't working, accusing the Government of "broken promises."
He will say: "Ministers told us that if we only accept the pain, recovery would come. Instead we have been mired in a double dip recession. They told us if we only accepted the cuts, our deficit would come down. Instead our borrowing is going through the roof.
"The biggest lie of them all was the cynical double talk that we are all in this together. The grim reality has been tax cuts for the richest with wage and benefit cuts for the poorest. Who can ever believe this shambolic, make-it-up-as-you-go-along Government?"
Unite general secretary Len McCluskey said: "People are already borrowing hundreds of pounds to get by each month. We know - and the government knows full well - that millions of low waged workers are just about keeping their heads above water.
"Yet this Government is going to crush their last vestiges of hope by attacking housing and income help. The poverty that will follow will engulf our communities for generations to come."
Grant Shapps, Conservative Party Chairman, said: "At today's march, Ed Miliband will be among friends - supporting his union donors who oppose every single one of our spending cuts. You can't be serious about clearing the deficit when you attend a march that calls for an end to austerity."