Fire Minister Brandon Lewis said firefighters should reconsider taking "completely unnecessary" strike action and that the move would be "baffling" to people who knew their pension terms.
The public will be baffled by the FBU's course of action when they hear that the deal being offered to firefighters gives them one of the most generous pension schemes in all the public sector.
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.
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Five people were killed and dozens more were injured after a car and knife attack in the capital on Wednesday afternoon.
Among those expected to attend the ceremony will be former US President Bill Clinton and ex-Northern Ireland first minister Peter Robinson.
Five people have been killed and 40 injured after a car and knife attack in London on Wednesday.