Marathon talks aimed at resolving the British Airways "swipe card" dispute were resuming again this evening.

Officials from the Transport and General Workers Union and Amicus talked with BA managers throughout last night at the London headquarters of the conciliation service Acas, adjourning at 6am.

Sir Bill Morris, General Secretary of the TGWU, said the talks had been "constructive" and would resume again at 5pm.

He said: "At the invitation of Acas, the T&G has been involved in exploratory talks.

"We have had an extensive examination of all the issues and the talks have been constructive.

"We have now adjourned and will resumed later today."

The third union involved in the dispute, the GMB, did not take part in the marathon session of discussions but is expected to be invited to join this evening's resumed talks.

ACAS is trying to avert a strike which could bring Gatwick's North Terminal to a standstill.

About 900 BA staff there have been advised by their unions to stay at their posts.

It is one of the busiest periods of the year and BA managers hope the dispute over new working practices will not escalate into a mass walkout.

Wildcat strike action has already caused misery for passengers at Heathrow.

Now ballot papers are being drawn up for a vote on official strike action at Gatwick.

At the centre of the row is a controversial electronic swipe card which BA employees must now use when they start shifts or take breaks.

Talks between management and unions broke down late on Tuesday after 27 hours of tough negotiation.

Gatwick staff were convinced by union bosses an official strike ballot was the best way forward.

BA managers feared a walkout as the deadline for when the cards became official management policy approached but check-in continued normally and flights boarded as scheduled.

One check-in agent said: "We just don't know what is going on. "

Staff were warned if they took unofficial action they could not be protected by union legislation.

Most of BA's ground staff at Gatwick are members of the T&G transport union.

Gatwick union organiser Madeleine Richards said: "We have urged our members not to put themselves at risk by taking unlawful action. "Members have contributed so much to BA to get the company through many difficulties over the past two years and are now facing unacceptable changes to their working practices."