Cabinet minister Christopher Pyne has stepped up the Turnbull government's attack on Labor over the ongoing citizenship crisis, calling for dual citizen MP Susan Lamb to quit this morning or face referral to the High Court.

As federal Parliament resumed on Monday, Mr Pyne foreshadowed a relentless focus on the Labor MPs with a cloud over their eligibility, indicating the Coalition was prepared to break with niceties and use its numbers to target opponents.

He confirmed the government would refer Ms Lamb - who holds the Queensland seat of Longman - if she did not quit of her own accord.

"She’s sitting in the House of Representatives and she is a citizen of the United Kingdom," Mr Pyne told ABC Radio National on Monday.