Premier Mike Baird committed to reforming the scheme on Thursday, making it as "generous as possible" and bringing it into line with protections for the NSW Police.

"We hope to have an agreement in place by the end of January," Mr Baird said after a meeting with more than 80 paramedics. "It is important we provide [paramedics] with the protection they need."

Health Services Union secretary Gerard Hayes welcomed the statement. But he said the Premier issued the statement even though union members declined to stop campaigning against him.

"There's a lot of 'trust me' in this," Mr Hayes said. "Our members were of the view that the campaign should continue. He wasn't happy [but] talk is cheap and we have been down this path before."

Union members have been chalking messages on the sides of ambulances including: "NSW paramedics most trusted, least protected, thanks to Premier Mike Baird."

Ambulance officers received letters instructing them to remove the slogans. The union had been called in before the Industrial Relations Commission to explain the messages.

Mr Baird's commitment follows a campaign against changes to paramedic compensation upheld by the industrial umpire two months ago and which the union had said would make paramedics more apprehensive about rushing into dangerous situations.

But Mr Hayes said the union might agree to change the tone of its campaign after the Premier's announcement.

"It might be, Mike Baird said he would do something about this in 90 days, then 89, then 88...," he said.

The change to the scheme was triggered by spiralling costs; premiums were found to have more than quadrupled. Paramedics help offset costs with a levy on their wages.

According to the union, paramedics receive only a maximum of two years' income support for disabilities incurred in the line of duty, compared to seven for NSW Police.

In 2011, police engaged in mass protests across NSW after the then O'Farrell government pushed ahead with plans to overhaul workers' compensation arrangements for NSW Police after costs of the scheme were found to have spiralled out of the government's control.

But the Premier said any changes to paramedic compensation would be backdated to August 2015, to cover the date at which the new scheme took effect.