The Musicians' Union has criticised a move which will force pubs, clubs and cafes to apply for entertainment licences for any form of amplified live music.
Many pubs and clubs feature regular live music
The ruling was pushed through the House of Lords on Thursday night after peers failed to defeat the government on the Licensing Bill.
It means that venues catering for audiences of 200 or fewer will have to obtain a licence to stage concerts - with the exception of unamplified ensembles such as string quartets.
The government says public safety is at risk from unlicensed events, citing more than 1,500 fires in pubs and clubs in England and Wales in 2001.
But the Musicians' Union says its artists are being singled out - while performers such as stand-up comics and novelty acts are exempt.
It argues that the measures will act as a deterrent to small venues wanting to host live bands.
Union spokesman Hamish Birchall said: "It's very disappointing that at the final hurdle we couldn't have secured some kind of exemption for small gigs."
He said the union would do "everything possible" to protect its members' interests.
A spokesman for the Department for Culture, Media and Sport said the law would be under constant review, and any evidence of a negative impact on live music would be considered.