The pop babe had been partying in a club to celebrate actress Chelsee Healey’s 25th birthday.
But as the group left the night spot, clubbers on the street outside appeared to be gorging on the dangerous legal high.
Many were breathing from balloons filled with the dangerous laughing gas, dubbed hippy crack.
Shocked N-Dubz star Tulisa was bundled into a taxi as she ended her night, leaving Chelsee and other pals behind.
More and more people are trying hippy crack, real name nitrous oxide, even though it can cause hallucinations, brain damage or even death.
Although the effects of the high last for only a few minutes, users say the sensation is similar to a hit of heroin or crack cocaine.
There is absolutely no suggestion that either Tulisa, 25, or Chelsee took the substance, which is legal.
And as the former X Factor judge left in a taxi after a night on the booze, other clubbers emerged and decided to carry on the party outside.
Pictures have emerged of canisters scattered across the floor.