A Labour government would negotiate “full tariff-free” access to EU markets for UK businesses after Brexit, Jeremy Corbyn is to say in a speech.

The Labour leader is expected to confirm his support for permanent membership of a customs union after the UK leaves the EU in March 2019.

He will also pledge to protect jobs and guarantee existing rights.

BBC political correspondent Ben Wright said the speech could force the government to change its position.

The prime minister has insisted the UK will leave both the single market and the customs union, allowing it to negotiate its own post-Brexit trade deals.

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But Theresa May is expected to give details on Friday of what has been agreed by her cabinet on how the UK’s “managed diversion” from the EU will work in practice.

In his speech, Mr Corbyn will argue that the EU is “not the root of all our problems” nor “the source of all enlightenment”.

“The truth is more down to earth and it’s in our hands; Brexit is what we make of it together,” he will add.

Labour could cause huge problems for the government

By Ben Wright, BBC political correspondent

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Brexit is not just a negotiation between the EU and the UK.

The British parliament has a huge role in this, more so now that the government doesn’t have its own majority.

Why this is now so significant is there are clearly a number of Tory MPs who agree with Labour that there should be a customs union after Brexit.

If – and it is still a big if, but a more likely one – Labour pass an amendment calling for the creation of a customs union, then it does cause huge problems for the government.

It would force the government to change its position.

That is why this is a really significant move by Labour.