Passport staff in Glasgow formed a picket outside their office

The Public and Commercial Services (PCS) union said 2,500 of its members supported the 24-hour walk-out.

The union estimated the action prevented up to 30,000 passports being issued on Friday, with most appointments being cancelled.

But the Identity and Passport Service dismissed the PCS estimate as "bizarre" and "a bit of a meaningless figure".

"Demand is not even that high at this time of year," a spokesman added.

All offices have remained open, and we have been able to continue offering emergency appointments Identity and Passport Service

"Our customers will not experience any delay."

Only half of the PCS members in the service took part in the strike, the spokesman said

"Contingency plans to minimise the impact of industrial action on our customers have worked very well," he added.

"All offices have remained open, and we have been able to continue offering emergency appointments."

The strike, which was backed by members by 3-1, was called in protest at delays to a pay settlement. It will be followed by a week-long work-to-rule from Saturday.

"We remain keen to resolve the pay issue as quickly as possible," the Identity and Passport Service spokesman said.

Passport price rise

Workers from London, Peterborough, Durham, Belfast, Liverpool, Glasgow and Newport all took part in the strike, said the PCS.

General secretary Mark Serwotka said the disruption caused by the strike action was "regrettable" but could have been avoided if managers had "made this year's pay deal a priority rather than cancelling negotiations".

"The magnificent show of support has illustrated the depth of anger over the delay in dealing with this year's pay," he said.

Earlier Mr Serwotka said staff were concerned they would see a repeat of last year's experience when it took management over a year to make a formal pay offer.

"Added to this is the fact that, at the same time as the cost of a passport has risen by 50% many staff members have seen their pay rise below the cost of inflation at a rate of just 1%."

BBC labour affairs correspondent Stephen Cape said the Treasury had still to decide how much cash was available for the pay settlement in a climate of tighter public spending.

He said there were similar wage problems in 19 other government departments, one of which could prove the next flashpoint.