Nobu—the sushi restaurant chain co-owned by Robert Deniro that caters to celebrities like Madonna, Leo DiCaprio and Sean Combs—has been busted in an undercover sting for selling critically endangered Atlantic bluefin tuna while concealing it from customers. Greenpeace sent spies to three London Nobu franchises, where they specifically ordered the near-extinction fish, and were told that the restaurants didn't stock it. But the cunning Greenies took their sushi back to the lab, where DNA tests revealed that the restaurants were indeed serving bluefin to moneyed gourmands. It's legal to serve bluefin, but people who claim to care about the environment—like Deniro, DiCaprio, Combs and Madonna—would supposedly never knowingly touch the stuff, preferring instead the less endangered, but less delicious, yellowfin. Which explains Nobu's sneakiness.

Nobu does not specify on its menus which species of tuna it serves. Requests for the information by campaigners have been met for several years with a terse "no comment".

Although it is not illegal to serve Atlantic bluefin, also known as northern bluefin, many chefs, including Gordon Ramsay, have dropped it because of concern that fishing is at higher levels than stocks can withstand. At Nobu Berkeley St, which has one Michelin star, investigators asked for Atlantic bluefin (hon maguro in Japanese) but staff told them the restaurant did not stock it. However, DNA tests proved that the fish they were given was indeed Atlantic bluefin.

[A] second dish they ordered, described only as "o-toro", the fattiest belly meat, was Atlantic bluefin. At Nobu London, a waitress told the investigators that a dish on the menu was hon maguro. The fish that was served tested positive as Atlantic bluefin.

The lack of clear information about the species of tuna on sale at Nobu could land the restaurants in trouble. A spokesman for Westminster city council said that falsely describing food was an offence.

Willie Mackenzie of Greenpeace said: "Nobu and Robert De Niro are clearly making a great deal of money serving up endangered fish." The restaurant declined to comment. [Telegraph]