Mariska Hargitay spent 30 years "living a lie"

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 - he denied her suspicion and she never mentioned Nelson to him again.

However, she went to see Nelson perform in Atlantic City when she was 30, and he cried when she introduced herself.

He told her: "I've been waiting 30 years for this moment."

But the 'Law and Order: SUV' star wanted to stay "loyal" to Mickey.

She recalled: "I went full Olivia Benson on him. I was like, 'I don't want anything, I don't need anything from you.... I have a dad.'

"There was something about loyalty. I wanted to be loyal to Mickey."

In the aftermath, Mariska struggled to cope with "knowing I'm living a lie my entire life" and questioned whether she had been a wanted child or "illegitimate" mistake, and if she was Hungarian or Italian.

The actress eventually bonded with Nelson and his daughters and began to understand Jayne had reconciled with Mickey because she knew he would offer them love and stability.

She tearfully said: "I grew up where I was supposed to, and I do know that everyone made the best choice for me," she says. "I'm Mickey Hargitay's daughter-that is not a lie.

"This documentary is kind of a love letter to him, because there's no one that I was closer to on this planet."

Mariska was keen to open up about her complex family background in the documentary as a way to "unburden all of us", and she had a private screening of the film with Nelson's daughters in Las Vegas.

She said: "They just wept and wept and wept. These two women that I love so much - I made them secrets! It's so heartbreaking to me."