A dispute over Covid-related safety at the head office of the Driver and Vehicle Licensing Agency has been going on for over 25 weeks, with threat of further strikes.
A coronavirus outbreak was declared at the DVLA's contact centre in December 2020. By the end of February this year, 560 Covid cases had been recorded amongst DVLA employees - working on site and from home - since September.
The union wants to see changes to the way the site is operated during the ongoing pandemic, like a further reduction in the number of staff working in the offices.
PCS general secretary Mark Serwotka said: "The determination of our members to secure a just deal remains steadfast.
"Ministers have admitted they scuppered the dispute-ending deal back in June, but they have underestimated our members' unbreakable resolve.
"We want a deal that has Covid safety measures at its heart, appropriate reward and recognition for staff working throughout the pandemic and a workplace recovery plan, agreed with the union.
"If our members vote once again for strike action, we will support them every step of the way."
A DVLA spokesperson said they were extremely disappointed to hear about the potential further strikes.
They said: "The safety of our staff is paramount. We have worked with public health bodies throughout the pandemic who have confirmed a high level of compliance and have no concerns.
"It is extremely disappointing that PCS continues to pursue unnecessary industrial action which will hold millions of motorists across the country to ransom."