On a turnout of 71%, that exceeded anticipated support, nearly 80% of those who voted among Prospect’s 1,000 members in the nation’s mapmaker supported strike action, while nearly 83% of voters were in favour of action short of a strike.

Staff will begin action short of a strike at OS sites across the country on Monday June 19. This will see staff work strictly to their agreed hours and a ban on unpaid overtime that OS depends on to keep functioning smoothly. The union is waiting to hear the results of a ballot of staff represented by its sister union PCS before announcing strike dates.

The action is in protest over a number of pay issues felt by staff over several years. In particular, a succession of below inflation pay increases, often non-consolidated, and the lack of a coherent mechanism for all staff to progress to the ‘rate for the job’.

Members are exceptionally angry that the findings of a joint management and union pay review, which aimed to identify and implement a fair and equitable pay system, have been ignored. Instead they have been presented with a ‘final offer’ of 3.8% in year one, and 3.6% in year two that will still leave large numbers of staff receiving consolidated increases below inflation or making little or no progress on progression.

Prospect negotiator Ben Middleton said: "Despite our members’ best efforts to negotiate a resolution to the pay problems, once again OS have ignored the need to resolve pay and equity anomalies within the system and left staff feeling overlooked and let down.

"This will be the first time staff have taken industrial action in the organisation’s 200-year history and demonstrates the high levels of dissatisfaction among our members in OS."

Prospect represents specialist grades in OS in a range of roles including cartographers, surveyors, marketing and sales personnel, designers, and IT engineers.