Temporary workers are starting to look, well, not so temporary.

Despite a surge this year in short-term hiring, many American businesses are still skittish about making those jobs permanent, raising concerns among workers and some labor experts that temporary employees will become a larger, more entrenched part of the work force.

This is bad news for the nation’s workers, who are already facing one of the bleakest labor markets in recent history. Temporary employees generally receive fewer benefits or none at all, and have virtually no job security. It is harder for them to save. And it is much more difficult for them to develop a career arc while hopping from boss to boss.

“We’re in a period where uncertainty seems to be going on forever,” said David Autor, an economist at the Massachusetts Institute of Technology. “So this period of temporary employment seems to be going on forever.”

This year, companies have hired temporary workers in significant numbers. In November, they accounted for 80 percent of the 50,000 jobs added by private sector employers, according to the Labor Department. Since the beginning of the year, employers have added a net 307,000 temporary workers, more than a quarter of the 1.17 million private sector jobs added in total.