Commuters have faced travel misery as a strike by London Underground workers caused chaos in the capital and sparked calls for changes to employment laws.

Members of the Rail, Maritime and Transport (RMT) union and the Transport Salaried Staffs Association (TSSA) mounted picket lines outside Tube stations as they continued with a 24-hour strike in protest at plans to axe 800 mainly ticket office jobs.

The walkout, which will continue until 7pm, led to three of London's 11 Tube lines being closed altogether while services on other lines were disrupted.

Transport for London said three quarters of Tube stations were open, including main centres such as Euston, Waterloo and Paddington, and claimed that more services were running than during a previous strike last month.

Union leaders contested TfL's claims, saying that the strike had caused widespread disruption and led to the suspension or part-suspension of services on all lines.

Meanwhile London's Mayor Boris Johnson will today tell the Conservative Party Conference in Birmingham that the laws on strikes should be changed so that at least 50% of union members would have to vote in a ballot before action was allowed.

Writing in The Daily Telegraph, Mr Johnson accused the trade unions, with Labour support, of pursuing a "nightmarish return to the politics of the 1980s" with "wave after wave of debilitating strikes".

He has accused the unions of mounting a "political attack" on the coalition Government.

RMT general secretary Bob Crow said: "The cuts to ticket offices, and safety-critical station staffing levels, that RMT members are fighting to prevent in the action today are the same cuts that Johnson opposed before he was elected London Mayor. To attack RMT and TSSA members standing up for Tube safety is hypocrisy of the highest order on the part of the Mayor."

The CBI also called for changes to employment laws. Deputy general secretary John Cridland said: "Unfortunately, current legislation often allows strikes to be decided by only a small proportion of the workforce. In this case, just 33% of balloted members supported the strike, only 17% of the total London Underground workforce."