London Underground services are set to be face significant disruption as the first of two 24-hour strikes by some Tube drivers begins at midday.

Members of the Rail, Maritime and Transport (RMT) union, which represents roughly half of drivers on the Tube network, are striking over a Transport for London’s (TfL) voluntary proposal to allow train operators to move to a compressed four-day week.

The RMT said the working day would be too long under the plans, risking driver fatigue and compromising safety.

TfL said the industrial action was “completely unnecessary” while Aslef, another Tube driver union, supports the deal as “exactly the sort every trade union should be trying to achieve”.