United Kingdom, May 18 -- Mariska Hargitay spent 30 years "living a lie".

The 61-year-old actress - whose mother, actress Jayne Mansfield, was killed in a car accident when she was a baby - was raised to believe the late Mickey Hargitay was her biological father but, after always feeling different from her siblings, she realised in her 20s that her dad was actually Italian entertainer Nelson Sardelli, who her mom had dated following a brief split from her spouse.

Recalling how she was shown a photo of Nelson and immediately realised he was her dad, she said in new documentary 'My Mom Jayne': "It was like the floor fell out from underneath me.

"Like my infrastructure dissolved."

But when she confronted Mickey - who passed away in 2006 ...