Government plans to make firefighters in England work until they are 60 and to increase their pension contributions have been backed by MPs.
The measure, which has led to a series of strikes by union members, was passed by 313 votes to 261 – despite a Labour attempt to throw out the scheme.
Fire Minister Penny Mordaunt said the pension scheme needed to be “fair to both firefighters and to the taxpayer”.
But the Fire Brigades Union says the scheme is unworkable and unfair.
It says it is unfair to expect firefighters who are 60 to have the same fitness levels as those in their 20s, warning some could be left facing the sack or with a severely reduced pension.
Before the vote, MPs on both sides of the House of Commons asked for assurances from the government that firefighters who failed fitness tests would be found alternative work away from the frontline.
Ms Mordaunt said protections for older workers would be bound by law and would mean that no firefighters over the age of 55 would lose their jobs for losing fitness through no fault of their own.
She said the average firefighter retired aged 50 following a career of 30 years but was expected to live and draw a pension for 37 years in retirement.
“It should come as no surprise to any member of this House that a pension scheme where the average member spends 25% more time in retirement than they do in employment is not sustainable,” she added.
The taxpayer had paid £370m in 2012/13 to top up firefighter pensions – a figure which was forecast to hit £600 million by 2019, Ms Mordaunt told MPs.
She urged firefighters to focus on adapting to change rather than being distracted by strikes, “scaremongering” and “divisive negativity”.
However, shadow communities secretary Hilary Benn said the proposals were “flawed”.
“The reason why these regulations are unfit is because ministers have drawn up regulations built on a flawed claim that all firefighters can maintain fitness, flawed because they can't tell us what the fitness standard is and because the assumption of fitness isn't safe,” he said.
“Ministers have claimed there is a guarantee firefighters who can't maintain their fitness and who can't be redeployed will receive an unreduced pension when documents show there is no such guarantee.”
The FBU has been in a lengthy dispute over the proposals scheme, leading to a series of strikes – most recently for 24 hours earlier this month.
The union said firefighters already contributed one of the highest proportions of their salary towards their pensions and had seen contribution rises over the last three years.
It said two thirds of firefighters would not be able to meet current fitness standard by the time they were 60.