PCS general secretary Mark Serwotka has said travellers could face months of airport disruption unless the Government comes forward with an improved pay offer for Border Force staff.

Travellers were warned by Border Force bosses to expect delays amid fears long queues at passport control could lead to people being held on planes, disrupting subsequent departures.

Around 1,000 members of the Public and Commercial Services (PCS) union employed by the Home Office to operate passport booths walked out on Friday at Heathrow, Birmingham, Cardiff, Gatwick, Glasgow and Manchester airports, as well as the port of Newhaven in East Sussex.

Speaking to BBC Radio 4, Serwotka said the strike mandate lasts right up until May.

“We think that the action at the borders is going to be very effective. We hope that the Government will therefore do the right thing and get around the negotiating table and put some money upfront,” he told BBC Radio 4’s Today programme.

“If not, we are raising money. We have a strike fund that means we can sustain this action. Our strike mandate lasts right up until May. We will be supporting this action up to May and we would re-ballot again if we have to.

“I think in January what you will see is a huge escalation of this action in the civil service and across the rest of our economy unless the Government get around the negotiating table.”

Military personnel have been checking passports at UK airports, helping to ensure passengers are not being delayed on the first day of Border Force strikes.

A Heathrow spokeswoman said: “The morning arrivals peak has started well.

“Immigration halls are free-flowing at Heathrow with Border Force and the military contingency providing a good service.”

A spokesman for Gatwick told the PA news agency: “Everything is going OK at the moment.

“There’s plenty of staff. The e-gates are all operating. It’s going well.

“There’s no delays as far as we’re aware, and no queues at the moment.

“I’m standing in arrivals and passengers are flowing through as normal.”

The Border Force strikes will take place every day for the rest of the year, except December 27.