Kenyan-born senator Lucy Gichuhi has provided the legal advice that backs her claim she is not a dual citizen, a government minister says.

READ MORE More MPs in firing line as citizenship crisis escalates

A constitutional law expert claims the senator did not automatically lose her Kenyan citizenship when she became an Australian citizen.

Advice from University of Nairobi professor Edwin Abuya says Senator Gichuhi should have written to Kenya's nationality affairs minister to renounce her Kenyan citizenship, News Corp has reported on Sunday.

Craig Laundy is backing his Liberal colleague.

"I take her at her word. It's there, it's public. I know there is a dissenting view, however, there's strong legal advice that supports her," he told Sky News on Sunday.

Asked if she should be referred to the High Court, he said: "not when all the information's now out in the public domain".

Senator Gichuhi included on the citizenship register a letter from Kenya's High Commissioner in Canberra, Isaiya Kabira, declaring she had not been recognised as a Kenyan citizens since 2010.

She nominated for the Senate in May 2016.

Labor frontbencher Brendan O'Connor said the senator's position was a problem for the government.

"It would appear on the face of it that if the legislation has to be read with the constitution, she may well be in some difficulty," he told ABC television.