Ms Lamb addressed the House of Representatives on Wednesday afternoon.
"I want to explain to the House why I can't obtain a copy of my parents' marriage certificate. It's a complex and a traumatic story, a story that I don't usually share," she said.
"One day when I was six years old my mum dropped me off at school and she never came back to pick me up."
On her declaration to Parliament's citizenship register, she lists her father's birthplace as Edinburgh, Scotland.
She lists her mother's as Mackay in Queensland and the United Kingdom for her paternal grandparents.
"The fact is, my mum is not around to grant me access to her marriage certificate and dad, he passed away nearly twenty years ago," she told the chamber after Question Time.
"That extra document the UK Home Office requested after they received my renunciation, my parents' marriage certificate, is a document I was advised I do no have a legal entitlement to claim."
The Queensland MP said the attacks on her family had become too hurtful to stay silent about her circumstances any longer.
She did not refer herself to the High Court, as other MPs under a citizenship cloud had done.
The government had been calling on her to refer herself or resign.
More to come
