As the TUC’s 150th anniversary congress opens in Manchester, the trade unions are once again facing the challenge of the 1930s and 1980s – can they nudge Labour to a place where they can springboard to power?

Labour was gifted a pleasant surprise by Theresa May with last year’s election but has not been able to build on that success as opinion polls stay stubbornly lower than that which is required for victory.

Trade unions are based on the principle of mutual solidarity and democratic loyalty. They have offered that to Jeremy Corbyn since 2015 but now are beginning to demand a say in Labour’s next direction of travel.

This is similar to the 1930s when the unions hauled Labour back from pacificism to a clearer sense of the need to defend European democracy.  In the 1980s Labour under the influence of Tony Benn and his aide, Jon Lansman, officially endorsed Brexit – leaving Europe – in its 1983 election manifesto. Unions pulled Labour back from this vote-losing dead end to supporting Jacques Delors and Social Europe against the Tory vision of economics and society in which employees had no voice or weight.

Last week’s NEC decision to put to bed the unnecessary summer horribilis for Labour happened because the unions told Corbyn it was time to adopt the international definition of antisemitism.

Now the decision of Britain’s second biggest private sector union, GMB, to support the call for a People’s Vote on Brexit allows Labour to get control of the Brexit debate instead of tailing behind Theresa May. The GMB has 640,000 members and sponsors 80 Labour MPs mainly in Labour industrial heartlands far away from London.

The GMB’s 80 Labour MPs join the 20 Labour MPs sponsored by the steel and textile workers’ union, Community and eight Labour MPs including John Cryer, the Chair of the Parliamentary Labour Party sponsored by the transport union, TSSA, which also urges a new vote.

And now the TUC general secretary, Frances O’Grady, has said the electorate should be consulted again over Brexit as more and more employees worry about their future of their jobs, which rely on just-in-time deliveries to and from the EU.