The rise in the number of self-employed people is not a sign of an entrepreneurial boom but is instead a worrying trend, MSPs have been told.
The Scottish Trades Union Congress (STUC) said the number of people working for themselves increased by almost 10% between 2008 and 2012. But eight out of 10 of those who became self-employed since the recession began work fewer than 30 hours a week.
STUC assistant secretary Stephen Boyd told Holyrood's Economy Committee: "The rise in self-employment through the recession is something we should all be worried about.
"The evidence suggests people are not making an enthusiastic choice to start working for themselves. They're trying to scratch a living doing what they previously did as employed individuals.
"They tend to be earning less. They tend to be working less hours, paying less tax. When you think of our current economic situation, it's not good to have people earning less and paying less tax."
Some may look at the rising number of self-employed people and "pretend this is reflective of an entrepreneurial boom in Scotland", but "we're just kidding ourselves", Mr Boyd said. He added: "At this point in time its a sign of economic weakness rather than strength."
The committee is investigating the problem of people working fewer hours than they want to and being unable to fully use their skills in their job.
Mr Boyd said: "There's 240,000 people in Scotland unable to work the hours that they want to work. That is not a good thing. For the economy as a whole, if we are under-utilising what we are told by politicians on a regular basis is our greatest resource, that is our people, then that is a problem."
In its submission to MSPs before the meeting, the STUC claimed that the Scottish Government's economic strategy does not sufficiently focus on the type and quality of any jobs being created.
A Scottish Government spokesman said: "The Scottish Government is doing all it can to strengthen our economy and create jobs by channelling funding into infrastructure projects, supporting economic growth, small businesses and entrepreneurship."