Tube workers will be balloted over taking industrial action in a row related to the firefighters' strike.

About 100 of London Underground's (LU) 15,000 staff refused to work during the two-day strike last week because of concerns over safety.

Officials at the Rail Maritime and Transport Union (RMT) are annoyed that they have not received assurances from LU that the people who refused to work will not face disciplinary action.

Bob Crow, general secretary of the RMT, said: "Tube bosses have failed to give us that simple assurance, and we have no alternative but to ballot our members for action."

Tube disruption

The RMT has notified LU that it will send ballot papers to 8,000 Tube workers next week. A result is due on 12 December.

During the firefighters' 48-hour strike LU reported that 96 drivers had refused to work.

The shortages led to the suspension of the Waterloo and City line on Thursday and of the Circle line on Friday.

Other services were disrupted or restricted because of staff shortages and 22 deep-lying stations were closed by LU following a safety assessment.