Firefighters in England and Wales staged a fresh strike today in a row with the Government over pensions and were said to be "digging in for the long haul".
Members of the Fire Brigades Union walked out for four hours at 10am - the fourth stoppage in recent weeks.
The union fears firemen and women will lose their jobs if they fail fitness tests as part of changes to the pension age from 55 to 60.
FBU general secretary Matt Wrack joined strikers at Westminster fire station in central London, one of a number of stations set to close in January under spending cuts.
He told the Press Association: "We are disappointed to be taking a fourth round of action, but the strike will be solidly supported again across the country.
"The Government has worsened its proposals which has only hardened attitudes among firefighters.
"We are determined to dig in for the long haul."
Mr Wrack said progress continued to be made in Scotland, where no industrial action is being held.
"The approach in Scotland is very different," he said.
The union has not ruled out further strikes.
Fire Minister Brandon Lewis said: "The FBU's fourth strike day contradicts its claims to want to resolve this dispute through negotiation, and further damages the good reputation of firefighters with the public.
"The offer on the table has significant advantages over the Scottish fitness principles that the FBU has already accepted. These proposals provide a firm basis for resolving this dispute. The FBU should call off the industrial action to continue discussions.
"Firefighters will still get one of the most generous public pension schemes. Less than a quarter of firefighters will see any change in their retirement age in 2015 and more firefighters' pensions are protected than in any other large public service workforce.
"A firefighter who earns £29,000, and retires after a full career aged 60, will get a £19,000-a-year pension, rising to £26,000 with the state pension. An equivalent private pension pot would be worth over half a million pounds and require firefighters to contribute twice as much."