More London Underground workers have voted to strike in a row over the new all-night Tube service as talks aimed at resolving the dispute began.

Members of the RMT and TSSA unions backed industrial action following a similar vote by drivers.

Unions and management are meeting at the conciliation service Acas, a week before a planned 24-hour walkout by members of the drivers' union Aslef begins at 9.30pm on July 8.

A strike by members of the three unions would cripple Tube services, causing travel chaos across the capital.

The unions are in dispute over pay and conditions for the new all-night Tube, which is due to start at weekends from mid-September.

The RMT said its members voted by 91% in favour of strikes and 96% for other forms of industrial action.

The union is also in dispute over a series of other issues including jobs and safety.

RMT general secretary Mick Cash said: "Balloting has concluded today in a series of disputes on London Underground, including the linked issues of pay and night running and also in the long running dispute over station staffing, mass job cuts and ticket office closures - each of the ballots has delivered an overwhelming mandate for action which will now be considered by the union's executive and a further statement will be issued by the union later.

"The industrial relations situation on the Tube has sunk to an almost unprecedented low with all four unions united and balloting for action over pay and working arrangements due to be ushered in under the guise of the mayor's "night Tube" vanity project in just 10 weeks' time.

"Casualisation, the attack on station jobs and the undermining of safety are all part and parcel of an overall cash-driven agenda coming right from the very top.

"It is simply outrageous that management, in a mad dash to bulldoze through the night running stunt, have smashed apart long-term agreements and have resorted to trying to bully staff into accepting roster changes at a local level, and the message from RMT and our sister unions is clear - we are not having it.

"These changes would also lock our members into a culture of anti-social hours and appalling working conditions that would rip apart work/life balance whilst at the same time they are being hit with pay proposals that would undermine their standard of living.

"RMT will be co-ordinating campaigning with our sister Tube unions as we seek to defend negotiating agreements, decent pay and the rights and working conditions of our members."

TSSA members voted by three to one in favour of striking.

General secretary Manuel Cortes said: "We hope that this result will show Boris Johnson (London Mayor) just how angry our members are at his plans to try and rush the start of the night Tube without any detailed agreement on manning levels.

"Under plans we have been shown so far, some Zone 3 stations will be left with just one staff member on duty in the middle of the night.

"That is no way to run a service which prides itself on safety and security.

"We want to reach a deal which safeguards both passengers and staff.

"We will be hoping to reach agreement on that in the coming days."

The vote in support of strikes was 76%, with 88% backing other forms of action in a turnout of 44%.

Steve Griffiths, LU's chief operating officer, said: "Londoners and businesses overwhelmingly back the night Tube. It will make life easier for everyone, cut journey times, create jobs and boost the economy.

"Most of our staff will not be affected by the new services at all because it affects only five of 11 lines.

"Some staff will actually work fewer nights than they do now because we have hired 137 more train operators specifically for the night Tube.

"The train staff who will be affected are being asked to work around an additional seven nights each year on average, with no increase in their total current hours. No one is being asked to work more hours.

"In return, we are offering a realistic pay increase this year and next, as well as an additional payment for night Tube working.

"We are ready to negotiate, but any increase must be sustainable and fair. I urge the trade unions to keep talking to us to achieve a settlement."