Image copyright PA Image caption Transport for London said the plans would save £50m a year

Two 48-hour strikes on the Tube will take place on 4 and 5 February, and 11 and 12 February, the RMT union has announced.

London Underground workers voted to go on strike in protest at plans to close ticket offices and axe 750 jobs.

Transport for London wants to close all ticket offices and have staff on platforms instead to save £50m a year.

Some 77% of Rail Maritime and Transport (RMT) union members voting in the ballot backed strike action.

Station staff will stop work from noon on both days, while drivers will not book on for any shifts between the hours of the action.

The last strike of this size was in November 2010.

The union also announced action short of strike, including telling its members not to sell tickets at certain times.

The transport authority is facing a budget reduction of about £78m in the financial years of 2013 and 2014.

It has said all stations would be staffed while services were running, with more staff being visible to help customers, and that there would be no compulsory redundancies.

The plans also include 24-hour service on five Underground lines.

Out of 3,356 votes cast, 2,567 were in favour of strike action.

The RMT said there was a 40% turnout, but London Underground said only 30% of RMT members took part and it urged union leaders to work with it to avoid disruption.

RMT General Secretary Bob Crow said the plans included axing "safety critical jobs" at a time when the Tube network was "under growing pressure from customer demand and needs more staff and not less to ensure safe and efficient operation".

'Criminals' paradise'

He said staff would also have to reapply for their own jobs, a process which would be "a kick in the teeth for the loyal and experienced Tube workforce who have kept services running safely and efficiently under constant pressure from weight of demand and a creaking and under-resourced infrastructure".

"These cuts would hit the vulnerable, the elderly, those with disabilities and women the hardest," he said.

"De-staffing stations, with supervisors running operations three stops down the line on an iPad, would turn the Tube system into a criminals' paradise where those with violence and robbery on their minds are given a clear run."

London Underground said less than 3% of all Tube journeys involved a ticket office payment.

Phil Hufton, chief operating officer, said: "We're clear that there'll be a job for everyone at LU who wants to work for us and be flexible, that we'll make these changes with no compulsory redundancies, and that we'll involve staff in our plans at every stage and support them through change."