In a post on Facebook, the Brindabella MLA said he was now in quarantine until he received further instructions from WA health authorities.

Canberra residents are free to travel to WA but under the state's border controls they must have not spent any time in NSW in the previous 14 days.

The state also requires travellers from "very low-risk" states, such as Canberra, to quarantine for a fortnight if they "knowingly" had contact with someone from a low or medium-risk state, such as NSW, in the 14 days before arriving in WA.

Mr Parton went to NSW on Boxing Day to call races at the Queanbeyan Racecourse.

He said he felt "pretty stupid". He said had only spent a couple of hours across the border and it hadn't crossed his mind when he flew to WA on January 4 to visit his mother.

Mr Parton's older brother posted photos to his Facebook page of the opposition transport, sport and housing spokesman reuniting with this mother later that night.

"To be honest, it simply hadn't occurred to me that I had 'travelled to NSW' when I flew into WA this week," Mr Parton said in the message posted to his page.

"Queanbeyan is just 10km from my house and at the end of the day I tend to consider it as a suburb of Canberra.

"When this came to my attention today, I immediately sought advice from the relevant authorities and am quarantining until I receive a response on next steps."

The Canberra Times sought comment from Mark Parton.

A Canberra Liberals spokesman responded on his behalf, saying at the time he filled out his WA travel permit, it was true Mr Parton had not been in NSW in the previous 14 days.

"However, a few weeks after lodging the application, he visited NSW less than 3km over the ACT border. Given the nature of the ACT/NSW border, it genuinely didn't occur to Mr Parton that he had 'travelled to NSW' when he arrived in WA," the spokesman said.

"Since this has been brought to his attention, Mr Parton has sought advice from the authorities and is currently quarantining.

"Mr Parton apologises for his error and is awaiting advice from the relevant authorities."

Mr Parton is understood to be planning to leave WA on Sunday, but his travel plans will hinge on advice from local authorities.

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Mr Parton said he had cancelled New Year's plans in Sydney to enable his travel to WA.

"I take COVID very seriously, and am very sorry for this oversight," he said.

WA Police said it did not comment on individual cases. However, it said any reported breaches of quarantine would be investigated.

A spokesperson for WA Premier Mark McGowan's office said "on the face of it" Mr Parton appeared to have breached WA's border controls.

"This is a matter for WA Police to investigate," the spokesperson said.

"Members of Parliament should be setting the right example."

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