The law must be changed to prevent the type of lobbying undertaken by David Cameron on behalf of the financier Lex Greensill, Labour has argued, after more details emerged about the extent of Greensill’s influence inside Cameron’s government.

Only external lobbyists who deal with the government are required to be on a formal industry register, and not so-called “in-house” lobbyists like Cameron, who took an advocacy role for Greensill Capital after leaving Downing Street.