Several hundred people gathered outside King’s Cross St Pancras station on Saturday afternoon for the Rail, Maritime and Transport union (RMT) rally.
It comes as RMT members walked out for the third time this week amid a row over pay, jobs and conditions, with little sign of a breakthrough in discussions between the union and rail operators.
Dozens of people held placards featuring slogans such as: “Tories out”, “Cut profits not pay” and “Support the railway workers’ strike.”
Meanwhile songs such as the Internationale workers anthem and Solidarity Forever played from speakers on a makeshift podium.
Ahead of the speeches, dozens of hospital workers and cleaners, with the support of the GMB general workers union, arrived in a show of support for the rail workers.
The staff from St George’s Hospital in Tooting Hill have been staging a week-long strike this week in a row over pay and conditions.
They arrived to cheers from the rail workers, with RMT president Alex Gordon announcing on the stage: “Welcome, victory to the cleaners.”
The hospital workers carried their own placards, which read: “#endoutsourcing” and “Out Mitie” – contractors who employ staff such as cleaners and caterers at 40 NHS trusts.
The group of hospital workers were calling for Mitie to be removed as the GMB union is calling for staff contracts to be taken back in-house by St George’s University Hospitals NHS Foundation Trust.
The crowds then heard from speakers including Labour MP Diane Abbott, actor and comedian Rob Delaney and disabled rights activist Barbara Lisicki.
During her speech, Ms Abbott said she gave the workers her “personal support”.
She added: “Above all I want to thank the RMT, its membership and its leadership for heading up the fight against this terrible Government.
“I also want to give a shout out to the GMB members who are in dispute at St George’s Hospital and I want to give them my personal support.”
Eddie Dempsey, assistant director general of the RMT, also addressed the crowds, saying: “We are being told in our industry that we must modernise and when they say we must modernise what they mean is we must be poor, we must lose our jobs and we must do that to protect the profits of private companies that have been robbing the British people for years.”
He said: “Enough is enough.”
“We think modernisation means you go to work and get paid a wage you can live on,” Mr Dempsey said.
“Our society is broken, our economy is broken and we are the people who are going to fix it.
“We say that if you are working class in this country, you deserve a house you can live in, a wage you can take care of your family on and protections when you get old.”
A Mitie spokesperson said: “Our people are what make our business exceptional and we are proud to offer industry-leading benefits. We are disappointed that GMB has decided to take part in this industrial action.
“We are always open to constructive talks in the best interest of our colleagues.”