Firefighters in Calderdale are currently taking part in a 24-hour strike.
The Fire Brigade’s Union (FBU) said the strike is part of a long-running dispute over pensions.
And it accused ministers of “misleading” parliament over what will happen to its members who fail fitness tests.
Matt Wrack, FBU general secretary, said: “Firefighters are outraged at the behaviour of the Westminster fire minister Penny Mordaunt and her boss Eric Pickles, who misled Parliament by falsely claiming that they had introduced a statutory guarantee that a firefighter failing a fitness test through no fault of their own would receive a full and unreduced pension.
“After investigation, it is now clear beyond doubt that no fire service employer agrees that any such guarantee exists. The response from the fire service employers have shown very clearly that Parliament has been misled to allow the government to force through attacks on firefighter pensions.
“Firefighters cannot accept these pension changes as they take no proper account of the real work firefighters do. It is outrageous that the only way the government could win a vote on this is by blatantly misleading MPs.”
The strike, which started at 7am today (Wednesday), will be followed by a period of action short of strike on tomorrow (Thursday).
West Yorkshire Fire and Rescue Service said cover is being provided by those not striking and by less qualified community response operatives.
Assistant chief fire officer Dave Walton said: “It is extremely disappointing that we once again find ourselves planning for yet another period of strike action by our firefighters.
“It is now 18 months since the first strike occurred and since then there have been 48 occasions when the people of West Yorkshire have not been protected by the normal level of highly skilled staff.
“There appears to be no end in sight to this ongoing and damaging dispute - each time a strike occurs the public are once again placed at risk.”
Firefighters last staged a strike over the same issue on December 9 last year.