Thousands of British ambulance workers will stage two further strikes on January 11 and 23 in an escalating dispute over pay and staffing, the Unison trade union said on Thursday, after a similar walkout by staff on Wednesday.

While Wednesday’s strike, which also involved workers affiliated to two other trade unions, lasted 12 hours, the two Unison strikes next month will last 24 hours each, Unison said in a statement.

The walkouts will involve all ambulance employees as opposed to just emergency response crews, although many will be exempted from strike action under emergency cover plans, said the union, which represents the majority of ambulance workers in Britain.

“It’s only through talks that this dispute will end,” Unison General Secretary Christina McAnea said. “No health workers want to go out on strike again in the new year.”

The strikes come as an already pressured health system faces further strain this winter, with nurses also going on strike in a separate pay dispute.

British health minister Steve Barclay said meeting unions’ pay demands would mean taking money away from frontline services.

“Strikes are in no one’s best interest least of all patients and I urge unions to reconsider further strike action before walkouts have a worse impact on patients,” he said in a statement.