The proposals mean that, for the first time, remote gambling is regulated at the point of consumption not the point of supply.
Paddy Power led the fallers with a 5.75 per cent drop, with Betfair losing 3.9 per cent, William Hill 3.7 per cent and Ladbrokes nearly two per cent.
Betfair switched its domicile to Gibraltar in March, following Ladbrokes and William Hill in setting up their gambling licences offshore. Paddy Power is headquartered in Dublin.
Penrose said: “Our new proposals are an important step to help address concerns about problem gambling and to plug a regulatory gap, ensuring a much more consistent and higher level of protection for those people in the UK who gamble online.