Lady Gaga was left "shaken" after a stalker got backstage at one of her shows.

The 'Bad Romance' singer's team were forced to call police after a woman forced her way into the holding area of London's The 02 during her concert last Thursday (16.12.10) and was found heading straight for the pop star's dressing room.

An insider said: "Gaga was understandably shaken by the incident but was a consummate professional and continued as per normal, putting on a dazzling show."

The obsessed fan - who was already known as a nuisance to the 24-year-old star's team - had gone to "great lengths" to get to Gaga and was found carrying forged backstage passes and laminates which helped her evade security measures.

A security source told the Daily Mirror newspaper: "This was a serious breach of security and the woman was heading in the direction of the stage and, more worryingly, Gaga's dressing room.

"This woman has gone to great lengths to produce all the fake documentation so she could move at ease in the holding area backstage."

The fan was detained by two members of security until police arrived to quiz her on site before letting her go.

The incident is not the only time security was breached during the 'Alejandro' hitmaker's current tour. On Monday (20.12.10) a fan reportedly grabbed her breast outside her hotel in Paris.