The Night Time Industries Association (NTIA) and hospitality bosses say they are ready to take the Government to court over its plan to introduce vaccine passports at event venues.
A letter to Health Secretary Sajid Javid warns such a plan runs the risk of discriminating against young people and some ethnic groups, who are less likely to be fully vaccinated.
Despite previously deciding that vaccine certification was more trouble than it's worth, the Government has started pushing through legislation to make vaccine passports mandatory in nightclubs and other crowded venues.
NTIA and others argue there is no legal definition of nightclub and question how nightclubs and "crowded venues" would be identified.
"Is it proposed that this be defined in some way, for example in terms of number of people admitted per square foot? What, if any, other types of venue are under consideration?"
NTIA is asking members to write to their MPs.