Rishi Sunak has not ruled out sacking NHS staff for not going to work during strikes under proposed new legislation.
Unions could be sued if they do not provide minimum levels of fire, ambulance and rail services, under planned anti-strike laws.
The Times reported that employers will also be able to sack staff under the new curbs to ensure minimum service levels in crucial services.
Asked if people could be sacked for not going to work in the health service, Sunak told broadcasters on Friday: “I fully believe in the unions’ role in our society and the freedom for them to strike.
“I also believe that that should be balanced with the right of ordinary working people to go about their lives free from significant disruption.
“That’s why we’re going to bring forward new laws, in common with countries like France, Italy, Spain and others, that ensure that we have minimum levels of safety in critical areas like fire, like ambulance, so that even when strikes are going on you know that your health will be protected.
“I think that’s entirely reasonable and that’s what our new laws will do.”
The prime minister also revealed that he had invited union leaders in for what he hopes will be a “grown-up” conversation on Monday about what is affordable.
He said he is “hopeful” that talks can be “constructive” and “we can find a way through this”.
Pressed on whether he could go a bit further with his pay offer to nurses, Sunak added: “We have always been clear that we want to have a grown-up, honest conversation, a two-way conversation with union leaders.
“That’s why the government has written, all departments have written to all their unions inviting them for talks on Monday so that we can have those conversations talking about what’s affordable, what’s reasonable, what’s responsible for our country.”
It comes as nursing union boss Pat Cullen said they are willing to meet the government “halfway” in the dispute over pay.
The head of the Royal College of Nursing suggested they would consider a settlement of about 10% if ministers agree to talks.
Cullen has previously said the RCN’s demand for a 19% rise, dismissed by the government as “unaffordable”, is just a starting point and she would put any new offer to her members.