Stephen Parry confided he might have a dual citizenship problem to senior colleagues including Cabinet minister Mitch Fifield months ago, but the ABC can reveal a colleague advised him not to raise the alarm.

Key points: Parry is understood to have raised his citizenship concerns with a Cabinet minister in August

Parry is understood to have raised his citizenship concerns with a Cabinet minister in August He is believed to have been told not to go public based on advice Barnaby Joyce and Matt Canavan would be fine

He is believed to have been told not to go public based on advice Barnaby Joyce and Matt Canavan would be fine Malcolm Turnbull criticised Parry for not speaking up earlier

Mr Parry, who on Thursday resigned as Senate president and as a senator for Tasmania following confirmation he was a British citizen, is understood to have raised his potential eligibility problem in mid-August.

That was about the time former Nationals deputy leader Fiona Nash told the Senate her father was born in Scotland, giving her potential eligibility problems.

The ABC understands Mr Parry saw similarities in his own situation and spoke to a Cabinet minister.

This minister is believed to have suggested he not go public because advice from the Solicitor-General was that other Coalition members like Barnaby Joyce and Matt Canavan would be cleared of citizenship problems.

Senator Fifield has confirmed to the ABC that Mr Parry mentioned to him "a few weeks ago" that he was checking his family history.

The ABC understands Mr Parry is upset his integrity has been called into question. ( AAP: Mick Tsikas )

"The onus is on all senators and members to satisfy themselves of their circumstances and I encouraged Senator Parry to do so," the Communications Minister said.

"He called me on Monday to say that he had sought advice from the British Home Office and had advised the Attorney-General of this."

When asked about the revelations, Treasurer Scott Morrison told 7.30 he had not had any discussions with Mr Parry about the former senator's potential dual-citizenship.

"I have no idea what that's about," he said.

"I never had any discussion with Stephen about these things. I mean, that's speculation, and people will try to kick up dust about this issue."

Mr Parry's colleagues are stunned he only revealed his own situation this week.

Prime Minister Malcolm Turnbull criticised Mr Parry for not speaking up earlier, saying he was disappointed the former senator did not make the issue public earlier.

"He chose to delay his reporting of it, he should have reported it much earlier and it could have been referred to the High Court together with the other matters that were dealt with, the other citizenship-by-descent cases," Mr Turnbull said.

The ABC understands Mr Parry is upset his integrity has been called into question and angry he is now facing criticism when he was advised not to say anything.

It is understood he feels betrayed and that his reputation is damaged.