Industrial action by London Underground workers will escalate from February 6 unless a dispute over jobs and ticket office closures is resolved, a union has warned.

The Rail, Maritime and Transport (RMT) union also decided a ban on overtime will continue as part of a “new phase” of action.

The announcement came minutes after the conciliation service said fresh talks will be held to try to resolve the row.

Acas announced LU has agreed to attend a meeting on Monday with the RMT and the Transport Salaried Staffs' Association (TSSA), whose members went on strike earlier this week, crippling Tube services and leading to travel disruption in the capital on the first full day back to work on Monday.

Talks were held at Acas last week and into the weekend but ended without agreement.

The unions are campaigning to have jobs reinstated and ticket offices reopened, saying cuts agreed by former London mayor Boris Johnson have gone too far.

The RMT said Tube management has conceded the 838 job cuts have had a “devastating impact” on passenger safety and numbers need to be increased.

General secretary Mick Cash said: “RMT members have shown this week they will not stand by while safety is compromised on London Underground off the back of cash-led cuts to staffing levels that the union has warned would have a serious, lasting and corrosive impact for staff and passengers alike.

“That is why our members have been forced to take this action.

“RMT members on the London Underground stations see day in and day out the toxic impact of the job cuts programme and they are reporting back that it is horrific.

“It has now also been shown at management level there is agreement with the union that the cuts have been a disastrous mistake and that the staff need to be put back on the stations.

“With the constant overcrowding on stations and platforms, it is only a matter of time before there is a major tragedy if we don't act decisively.

“Our dispute is about taking action to haul back the cuts machine and put safety back at the top of the agenda.

“Today’s decision gives ample time for London Underground to come forward with the serious package of proposals now required to kick-start the negotiations.

“The union remains available for talks.”

Steve Griffiths, London Underground's chief operating officer, said: “We look forward to resuming talks at Acas on Monday in order to make progress towards resolving this dispute.”