The TUC said more than two in five new jobs created since mid-2010 have been self-employed.
Workers aged over 50 have accounted for half the increase in self-employment, but there has also been an increase among pensioners, part-timers and "odd-jobbers", the research found.
The TUC said it was concerned that many people were taking self-employed work because they could not find good quality jobs.
The number of people starting their own business has fallen in recent years, according to the TUC.
General secretary Frances O'Grady said: "Self-employment accounts for almost half of all the new jobs created under this government.
"But these newly self-employed workers are not the budding entrepreneurs ministers like to talk about. Only a tiny fraction run their own businesses, while the vast majority work for themselves or another employer - often with fewer rights, less pay and no job security.
"While some choose to be self-employed, many people are forced into it because there is no alternative work. The lack of a stable income and poor job security often associated with self-employment makes it hard for people to pay their bills, arrange childcare, plan holidays or even buy or rent a home.
"The economy is finally back in recovery yet people's wages are still shrinking and many are unable to find stable employment. Until we see decent pay rises and better job security, working people will continue to feel that the recovery is passing them by."
The report was published ahead of the latest unemployment figures on Wednesday.