One in five working men's clubs in England and Wales fears it will be forced to close as a result of the smoking ban coming into force within the next few weeks, according to a poll.
Of 560 clubs surveyed for the BBC, more than four out of five (83%) thought takings would fall as smokers stayed away.
And 20% said they believed their club was "quite likely" or "very likely" to close.
The ban will start in Wales on April 2 and in England on July 1 and will prohibit smoking in pubs, clubs and enclosed public spaces, even if the area is only open to private members.
The Government originally wanted to exempt private clubs, but was overruled by the House of Commons.
The general secretary of the Club and Institute Union, Kevin Smyth, said the ban came on top of an increasing burden of red tape on clubs.
He told the BBC Radio 4 Today programme: "Gaming permits, extra increases in licensing fees and now another set of legislation which looks as if it will almost certainly reduce the number of members coming into clubs is a great concern.
"I can understand why a number of clubs feel this may be the straw which breaks the camel's back."
Just 1% of the 560 clubs taking part in the survey thought their takings would rise as a result of them becoming smoke-free.
A quarter thought the ban would be difficult or near-impossible to enforce and 40% were confused about the public spaces covered by the ban.
