A buffer zone preventing anti-abortion protesters from holding vigils outside the clinic was introduced in March. It was designed to prevent patients from being harassed and intimidated.

Fines of up to $3750 can be handed out for protesting in the exclusion zone, while those who take video or photographs of people entering or leaving the clinic can attract fines of up to $7500, or six months in jail.

But the buffer zone was not large enough to prevent protesters from getting in the line of sight of patients entering the clinic.

That has forced the government to announce an extension, which will include any areas accessible by the public in 1 Moore Street, the ACT Health building, as well as surrounding blocks.

The larger buffer zone will include Rudd Street, West Row, the alleyway of Odgers Lane, and surrounding roads, footpaths, gutters, outdoor areas, and underneath a "building's facade".

It comes into effect on Thursday.

Health Minister Simon Corbell said the original zone had "unfortunately" allowed anti-abortion protests to continue on the fringes of the zone, keeping them in the line of sight of patients.

"We gave an assessment at the time as to the desirable area that needed to be the protected area," he said. "Operational experience has highlighted that it would be wise to make these relatively minor adjustments to ensure that there aren't opportunities for protest or other behaviour that would impact on the centre."

The decision came after the first person to be fined, 75-year-old Kerry Mellor, had his criminal infringement notice withdrawn by police.

After earlier announcing his intention to challenge the $750 fine, Mr Mellor wrote to ACT Policing disputing both whether he was within the exclusion zone and whether his behaviour - praying - amounted to "protest".

A delegate of the chief police officer told Mr Mellor police had decided to withdraw the notice due to "ambiguity" around the "boundaries of what comprises a 'protected area'".

"I am satisfied that your activity on 15 April, 2016, did not take place within the protected area and no offence was committed," the delegate wrote.

That Friday, Mr Mellor was with seven others who had gathered to hold a prayer vigil opposite the ACT Health building in Civic.

On the advice of police, most of the group moved to the entrance of Odgers Lane, just outside the exclusion zone. But Mr Mellor refused to move from his position outside the PJ O'Reilly's pub.

Mr Mellor says he didn't obey police because he didn't believe he had committed an offence under the new laws banning protests in the zone.

"Our central point is that we are taking part in public prayer, we are not engaged in a protest. We don't hand out any literature, we don't talk to passersby," he said. "We don't say anything to anybody except God."

But in expanding the exclusion zone, Mr Corbell said, "protesting or behaviour that increases emotional distress or may prevent women from accessing legal and medically recognised health procedures is prohibited within the defined protest-free zone".

Mr Mellor said the group had continued to gather each Friday morning but had not been approached by police since. He said he would continue to pray within the exclusion zone.

First introduced in Tasmania in 2013 and followed by the ACT, Victoria has fast-tracked exclusion zones, and NSW is looking at similar laws.