The fire brigades' union's call for a 40 per cent pay rise is "unrealistic", the prime minister said yesterday.

Tony Blair said the pay demand would have a "terrible" effect on the economy and lead to similar demands from other public sector workers.

He said: "The first thing that would happen is that the Bank of England would start putting people's mortgage rates up."

The union revealed that unofficial strike action was already affecting parts of Britain. Up to 30 brigades are only answering emergency calls and are refusing to carry out other duties.