The 42-year-old allegedly only had a business class ticket and lost it when she was refused entry to the lounge.
According to reports, eight armed police officer had to destain the reality TV star as she pulled her hair extensions out in anger.
An eyewitness told The Sun: "She had completely lost all control and she was screaming at officers.
"They had no choice but to arrest her for her own and everyone else's safety."
Another said: "She went ballistic, she screamed 'I can't f****** believe you are treating me like this'."
Following her arrest, Tara was reportedly taken to a West London police station where she was cautioned under the Public Order act.
A spokesman for Scotland Yard said: "Police at Heathrow Terminal 5 were made aware of a disturbance in the forecourt of the building at approximately 3.30pm on Saturday, December 20.
"Officers arrived at the scene and arrested a 42-year-old woman. She was taken to a West London police station and subsequently accepted a caution under section 5 of the Public Order Act 1986."
Tara later dismissed claims she was drunk at the time of her arrest. She said: "I wasn't drunk, there was no disorderly. I was cautioned, I saw a doctor, they were nice to me."