Driving examiners in England, Wales and Scotland are to stage a 48-hour strike the day a new driving test is launched.
The Public and Commercial Service (PCS) union warned thousands of tests could be cancelled when up to 2,000 members take part in the 4 December walkout.
It said examiners, who are employed by the Driving and Vehicle Standards Agency (DVSA), were being told to work harder as the tests come into force.
The DVSA has said the new test would better assess safe driving skills.
The new-look test means learners will need to follow directions from a sat nav and drive into a parking space.
Examiners will need to ask the candidate vehicle safety questions while on the move, while the test contains 20 minutes of independent driving instead of 10.
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PCS union members voted by 84% in favour of striking, on a 70% turnout.
The union has called for the new driving test to be suspended pending a full safety review.
Mark Serwotka, PCS general secretary, said the government was trying to force "detrimental changes" on its members with the new test.
The union questioned the safety of testing sat nav use, saying "incidents occurred on driving lessons which have been conducted to the new testing arrangements".
It added that requiring examiners to carry out seven tests a day - at one hour two minutes per test - should be limited to six tests.
'Scrap' new test
"Our members, whose jobs are about ensuring our roads are safe for drivers and pedestrians, have voted overwhelmingly to demonstrate that these changes are unacceptable," Mr Serwotka said.
It said members will work-to-rule from 23 November, where instructors stay at work but do exactly what is stated in their contracts, with a ban on overtime.
The DVSA said the new test would better assesses a driver's ability to drive safely.
Mr Serwotka called on the government to "avoid this strike action by instructing their officials in the DVSA to scrap the plans and re-enter serious negotiations with PCS".
But Steve Gooding, director of the RAC Foundation, warned that thousands of candidates could be "left fuming" if tests are cancelled.
He said: "Some 1.7 million people in Britain took a driving test last year which suggests around 10,000 candidates could be left fuming if this strike goes ahead.
"We hope a deal can be done to implement the new test to everyone's satisfaction so this industrial action can be called off."