The Driver and Vehicle Standards Agency has said it will provide an update as soon as it can on any impact if workers go on strike.
More than 1,900 members of the Public and Commercial Services union (PCS) at the agency are being balloted for strike action.
PCS members who carry out driving tests and approve people to be driving instructors are in a dispute with management over plans to reduce the backlog of tests.
DVSA chief executive Loveday Ryder said: “I am incredibly grateful to DVSA colleagues for the outstanding job they do in keeping roads safe and delivering for our customers. But it is disappointing that the PCS has decided to ballot its members.
“We will update customers on any impact on our services as soon as we can.”
The DVSA said it was taking measures to reduce driving test waiting times including putting all eligible managers and administrative staff back on the front line to do driving tests full-time for six months, and recruiting new driving examiners.
The agency said waiting times are long due to an increase in demand and sustained industrial action in the dispute over civil service pay.
DVSA ‘disappointed’ as workers balloted for strike action