London Underground tube drivers have voted to go on a 24-hour strike despite being offered a 0.75% pay rise and a £500 bonus after they were asked to work nights.
Aslef, the union which represents some Underground drivers, also turned down a £250 bonus for its drivers.
A date and time of this proposed strike has not been confirmed.
The other unions, the Rail, Maritime and Transport Union (RMT) and TSSA, are due to hold a ballot on strike action later in the month.
Under Transport for London plans, from 12 September, Londoners and visitors to the city will be able to travel on the Jubilee, Victoria and most of the Piccadilly, Central and Northern Tube lines all night on Fridays and Saturdays.
Night Tube - as the scheme is known - was put forward to cope with increasing demand for tube journeys on at the weekend.
By 2017, night services could operate on London Overground services and four years later on the Docklands Light Railway.
Night Tube services will also be expanded to the Metropolitan, Circle, District, and Hammersmith and City lines once modernisation has been completed.
The changes would bring the famous London Underground network in line with the New York metro service, which operates around the clock.