Tulisa, 27, was quizzed by police after she crashed her Ferrari into another car outside Southgate tube station on Thursday – and allegedly failed a breathalyser test.
But sources close to the former X Factor judge insist she’d only had one drink at home before going out to the shop.
An insider told the Mirror: “Tulisa had just one drink, a vodka, and it was only a few minutes earlier – but she needed to pop to the shops for a few bits.
"She was careful not to have another drink and jumped into the car."
They continued: “By the time she was breathalysed it was about 20 minutes later and she was confident that she would pass the test. But the machine flickered right on the brink before coming back positive.
“At the police station she gave a second sample after insisting she wasn’t over the limit. She is completely convinced she hadn’t drink too much to drive. Now she has to wait to find out the results of that sample.”
Last year Tulisa was involved in drugs sting last year, when undercover reporter Mahmood Mazhar recorded her claiming she could ‘score’ him £800 worth of cocaine.
But the court case collapsed when the judge revealed he had reason to believe Mahmood lied during the pre-trial hearing.
It is thought that Tulisa has been back in touch with the lawyers she worked with during that trial in a bid to clear her name once again.