Labor MP Susan Lamb has opened up about the "deeply personal" moment when she was six years old and abandoned by her mother, but the Turnbull government still believes she should quit Parliament as she is a dual UK-Australian citizen.

The Queensland-based MP for Longman has previously said that she and her mother, Hazel Cant, are estranged and that she had taken the “reasonable steps” required to give up her British citizenship.

Ms Lamb is a British citizen through her father and she began the process of renouncing her UK citizenship about two weeks before nominations for the 2016 election closed; her application to renounce her British citizenship was rejected by the UK Home Office because she did not provide a copy of her parent’s marriage certificate.

She has indicated that she was unable to obtain the certificate because under Queensland law if a parent is alive - as her mother is - they must give permission for the marriage certificate to be released. Turnbull government sources disagreed with this assessment.