Unions warned the UK could face a general strike this year as rail workers voted for fresh action set to intensify a summer of industrial unrest. The vote for further transport strikes came as Keir Starmer sacked shadow transport minister Sam Tarry who conducted broadcast interviews alongside striking RMT workers at Euston station – a move that is likely to increase divisions between Labour and trade unions. Other shadow ministers are expected to escape serious sanction but Tarry was told by Labour whips he had broken collective responsibility by making statements about pay and inflation that are not party policy. Senior shadow ministers have expressed private concern at Starmer’s policy not to allow frontbenchers to join picket lines – saying it could become unsustainable with unprecedented levels of industrial action in the offing. As much of Britain’s rail network ground to a halt, the Rail, Maritime and Transport (RMT) union chief, Mick Lynch, called for a general strike in retaliation to ministers’ threats to curb industrial action, warning of “the biggest resistance mounted by the entire trade union movement”. Travel was disrupted for millions on Wednesday as some lines closed and only about one in five trains ran on about half the network, as a fourth day of pickets this summer affected the network in England, Scotland and Wales. Aslef, the train drivers’ union, announced it had an overwhelming mandate for further industrial action which will involve drivers walking out at nine rail companies in a dispute over pay. A total of 974 drivers at CrossCountry and Avanti – 93% – voted in favour of a strike on 13 August, adding to actions already scheduled for that Saturday by drivers at Greater Anglia, Great Western Railway, Hull Trains, LNER, London Overground, Southeastern and West Midlands Trains. “We’ve been forced into this position by the companies, who say they have been driven to this by the Tory government,” said Mick Whelan, Aslef general secretary. “We want an increase in line with the cost of living – we want to be able to buy, in 2022, what we could buy in 2021.” Tarry, a former officer of the TSSA trade union who helped run Jeremy Corbyn’s leadership campaign, was removed from his post on Wednesday afternoon, though sources described his actions as goading Starmer to sack him in order to help him with a re-selection battle. Advertisement The Guardian understands Tarry was told he was sacked for saying that it was “not acceptable to offer below inflation pay rises” because it would be a real-terms pay cut for workers. Tarry was told that Labour’s position was that it was for ministers and unions to negotiate terms. That dispute is likely to cause significant alarm from trade unions about Labour’s position, including those affiliated to the party. On Wednesday RMT members at Network Rail and 14 train operators walked out alongside members of the Transport Salaried Staffs’ Association (TSSA) at Avanti West Coast. Both unions are planning strikes on 18 and 20 August, while the RMT announced a strike on London Underground on 19 August Lynch also said he would campaign for the Trades Union Congress to call a general strike if Liz Truss became prime minister in September and pressed ahead with anti-union plans. Truss and her rival Tory leadership candidate, Rishi Sunak, have said they will ban strikes on essential public services like the railways, and Truss has said she would legislate for minimum service levels on critical national infrastructure in the first 30 days of government. “It is completely wrong that the travelling public are being held ransom by militant unions,” Truss said on Tuesday. “I will take a tough line on trade union action that is not helping people get on in life.” Responding to the comments, Lynch said: “The proposals by Liz Truss amount to the biggest attack on trade union and civil rights since labour unions were legalised in 1871. Truss is proposing to make effective trade unionism illegal in Britain and to rob working people of a key democratic right. “If these proposals become law, there will be the biggest resistance mounted by the entire trade union movement, rivalling the general strike of 1926, the suffragettes and Chartism.” Asked if it would call a general strike, the TUC stressed “every strike is a democratic process”, but said: “It’s clear this Conservative government is not on the side of working people.” The RMT has rejected a 8% pay offer spread over two years from Network Rail as “measly”, saying that it is not close to current inflation. The offer is conditional on changes to working practices, rules on redundancies and work-life balance, the union said. The RMT opposes proposals to close ticket offices as more journeys are booked online, amalgamate pay grades, and change pensions arrangements. Advertisement Andrew Haines, the Network Rail chief executive, said: “Despite our best efforts to find a breakthrough, I’m afraid there will be more disruption for passengers this week as the RMT seems hellbent on continuing their political campaigning, rather than compromising and agreeing a deal for their members.” The transport secretary, Grant Shapps, ruled out meeting unions to break the deadlock, even if the situation escalated, saying he was “not the right person to be in the room negotiating”. Lynch said the only way he could think of settling the current pay dispute beyond strikes was “trial by combat”. “I can’t think of [another] way at the moment because we’ve been negotiating for two years,” he said. “But it would be interesting if me and Grant Shapps went head to head, if that’s not too flippant.” Road congestion levels were up in cities and rail passenger numbers were two-thirds down on a normal Wednesday. But more people ventured on to the railways than on 23 June, the second day of the last round of strikes, Network Rail said, suggesting the public may be adapting to the industrial action after four strike days in quick succession.