About 250 social workers went on strike on Monday against the government's extradition proposal.
Labour Party lawmaker Fernando Cheung, who used to represent the social welfare sector, and a group of welfare workers staged a protest at Southorn Playground in Wan Chai.
They demanded that Chief Executive Carrie Lam withdraw the controversial extradition bill.
Cheung said those who walked out would be out and about, offering assistance to other anti-extradition protesters.
He also said the government should hold dialogue with the opposition to help resolve the crisis.
Cheung also warned that welfare sector workers would continue their strike, if police use force to clear protesters.
One of the groups taking part in the strike, the Reclaiming Social Work Movement, said its members would be patrolling the area near the government's headquarters to help those stopped and searched by police.
The group's spokesman, Lemon Fok, expressed fears that their rights may be violated.
"We heard on the news that when some young people were stopped and searched, it's quite different from the usual practice of the police. We worry that the rights of those young people are being harmed," he said.
Despite the work stoppage by social welfare employees, earlier calls for a major strike and class-boycott campaign failed to materialise in Hong Kong on Monday.