Dining venues have been warned they could be losing trade by using Parmesan cheese in too many dishes.
Parmesan is not suitable for vegetarians as Parmesan/Parmigiano-Reggiano is an EU Protected Designation of Origin product and has to be made using calf rennet.
Therefore, venues using the cheese in "vegetarian" dishes as a garnish or ingredient are excluding vegetarians and vegans.
Charity the Vegetarian Society has launched a campaign called Say Cheese highlighting that Parmesan is not vegetarian.
The society has produced cards for veggies to leave behind at restaurants or to send before visiting one.
"Many restaurants have only one or two veggie options on a menu," said Katie Douglass, head of catering services at the charity. "Often both of these are then ruled out as they use Parmesan.
"Restaurants could make it so much easier for themselves by leaving the cheese off, or using an alternative and labelling it as such."