New restrictions will be introduced on strikes in essential services if the Conservatives win next year's general election, David Cameron has said.
Mr Cameron said he intends to introduce a minimum threshold on the number of employees who must take part in a ballot on industrial action before it can trigger a strike.
The Prime Minister said he had been held back from introducing a threshold of this type since he took office in 2010, because of opposition from Liberal Democrats in the coalition Government.
His comments come after a disruptive strike on the London Underground at the end of last month.
Mr Cameron told BBC Radio London: " Of course there is a right to strike in our country, but in essential services, isn't it worth saying that there ought to be a threshold, a certain percentage of people who have to take part before a strike is called that does so much damage.
"This is not something I can deliver in coalition. Our Liberal Democrat coalition partners don't seem keen on this, for whatever reason. But I am keen on it, and a new Conservative Government would deal with that."
TUC general secretary Frances O'Grady said: "Knee-jerk anti-unionism is to election campaigns as umbrellas are to the British summer.
"But the Prime Minister should remember that Britain already has some of the toughest anti-strike laws of any democracy.
"Public sector workers will conclude today that this Government is planning to hold back public sector pay for the foreseeable future and wants to stop those affected having any voice."