The general secretary of Britain’s biggest trade union has called for restrictions on the free movement of people moving between Britain and the European Union to work.

Len McCluskey, who is seeking re-election to his post in a contest to be held next year, said at the launch of his campaign that there should be “safeguards” against a competitive race-to-the-bottom.

“Unions understand that workers have always done best when the labour supply is controlled and communities are stable. While we must reject any form of racism, and help refugees fleeing war, we must also listen to the concerns of working people,” he wrote in an article for the Huffington Post website.

“They understand that the free movement of labour means downward pressure on wages, in some sectors at least.

“That’s why I have called for new safeguards that would ensure any employer recruiting from abroad must be covered by a proper union or collective bargaining agreement, stopping companies cutting costs by slashing workers’ wages and transforming a race-to-the-bottom culture into a rate-for-the-job society.”

The plans echo a call last month by Clive Lewis, the shadow business secretary and an ally of Labour leader Jeremy Corbyn, who suggested that employers recruiting from abroad should have to be a member of a trade union.

Labour, whose biggest single donor is Unite, is split on the issue of freedom of movement, with Mr Corbyn and shadow home secretary Diane Abbott supportive of its continuation and some MPs critical of it.

Mr McCluskey said in a campaign video that Brexit had to be good for workers, and pledged to fight for a better deal.

“In all the talk of ‘hard’ and ‘soft’ [Brexit], of market access and so on, workers need to know that someone is looking out for them,” he said.

“We are putting protecting jobs, as at Nissan, and workers’ rights at the top of the agenda – but that work is just starting.

“We can’t let the City and the CBI settle our economic future without hearing from working people.

“Second, the emergence of the ‘gig economy’ – the age-old problem of a casual labour market, now reaching epic proportions in Britain. That millions of workers have no security and few rights is a blight on British society.”

“The trade union challenge is to offer these workers the same protections as we do to those in better-established industries.

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“Unite will be in the forefront of legal and political campaigns to end the abuses of the ‘flexible’ labour market.”

At the Scottish National Party conference earlier this autumn Frances O’Grady, the general secretary of the Trades Union Congress, suggested that trade unions should be represented in Brexit negotiations in order to ensure that any settlement was good for workers.

Mr McCluskey was elected as general secretary in 2013. The more moderate, Labour-aligned candidate for the trade union’s leadership, he beat far left-backed candidate Jerry Hicks in the contest by 64 per cent to 35 per cent.