An investigation by Which? has discovered 40% of lamb takeaways had been contaminated with other meats, with some containing no lamb at all.
Of 60 samples tested in London and Birmingham, 24 had been mixed with other meats.
In the aftermath of the 2013 horsemeat scandal, Which? is running a campaign to stop food fraud.
It's calling for local authorities need to deliver food law enforcement effectively and efficiently, for the Food Standards Agency needs to ensure there is joined up action at a national and local level that prioritises consumers' interest, and for the Government to implement the recommendations from the Elliott Review on horsemeat.