The Government has been accused of opening up a "market free-for-all" by handing over large slices of public services to private firms.
The TUC said there was growing opposition from the public and among workers to the privatisation of services, especially in the NHS and education.
The union organisation pointed out that the Government's Work Programme had ended up in the hands of private companies, with 35 out of the 40 prime contracts awarded to large businesses.
In a paper sent to the Government, the TUC said a market-led approach to reform was increasing the private sector takeover of public services.
TUC general secretary Brendan Barber said: "We know that public services need to keep track with changing times, but handing over large slices of services to private businesses does nothing but undermine accountability, local responsiveness and choice.
"The Government's rhetoric doesn't match the reality and it has created a credibility deficit."
The TUC suggested an alternative model of reform, based on collaboration between the public sector, voluntary groups and charities.
Mr Barber added: "No wonder we've heard so little about the Big Society from the Prime Minister lately - it's clear that the reforms being implemented by this Government have little to do with charities or voluntary providers."
