The UK Door Security Association (UKDSA) said a shortage of door staff will cause delays to clubs opening later this year.
The association said after a year of closure many security staff have moved into other work and some staff who are not UK nationals have returned to their home countries following Brexit and the pandemic.
The UKDSA is now calling for new, more rigorous training regulations, due to come in in April, to be postponed to help agencies recruit new security staff more quickly.
From 1 April security staff must have first aid qualifications before taking the training required to be a door supervisor, according to the Security Industry Authority, the government's regulatory body for the sector.
There are additional training requirements related to terror threats and emergencies, the use of body-worn video recorders, and breathalysers. Some of the new requirements start in April, some in October.
The UKDSA said it supported the additional elements in the new training regime but said it was "deeply concerned about the timing of these changes and the impact on front-line staffing levels".