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Jeremy Corbyn will set out Labour's vision for Brexit in a key speech.

Yesterday the Labour leader slammed Theresa May for her "waffle and empty rhetoric" over Brexit .

But critics of the Labour leader have used similar attacks on his own position.

Time and again Labour has struggled to set out how their support for a "jobs-first Brexit" would actually work in practice.

The Labour leader will use a speech on Monday to set out what his party wants to see from the UK's future relationship.

And today Corbyn's right-hand man John McDonnell indicated that Labour's Brexit policy was 'evolving'.

Speaking at a thinktank the shadow chancellor reinforced support for 'a' customs union rather than 'the' customs union.

He said: "The reason we’re saying ‘a’ customs union is because we don’t want the same asymmetric relationship that Turkey have got.

"What we would want is to negotiate around our ability to influence the trade negotiations that would take place on behalf of us all - both ourselves and European countries - in terms of trade via a customs union.

"That would be the discussion we would want to open up."

Corbyn's speech comes amid mounting pressure from Labour MPs, MEPs and members for a softer approach to Brexit.

Yesterday Mr Corbyn led on Brexit at Prime MInister's Questions showing that he is more comfortably attacking an issue he is often accused of ignoring.

His line of attack on Northern Ireland, where the only obvious answer to the border question is remaining in a customs union, suggested Labour is nearer to adopting this as official policy.

(Image: Manchester Evening News)

Labour's shadow Northern Ireland secretary and Remain supporter Owen Smith signalled Labour's position may be softening in an interview yesterday.

Asked if he had clashed with the leader he replied: "No, I think Jeremy's position is evolving and deepening."

While at the beginning of the week Mr Corbyn he told the EEF conference: "We have to have a customs union."

Labour's leadership has come under pressure from the Remain-supporting unions but also increasingly from the party's membership who overwhelmingly back staying in the single market and customs union and whose role within the party has been strengthened under Corbyn's leadership.

A source told the Daily Mirror Mr Corbyn's speech will involve fleshing out Labour's ideas about Brexit and how it feeds into their wider plans to transform the economy.

It will put Theresa May under further pressure as she struggles to contain the threats from the right of her party.

Eurosceptic Tories tightened the screws on the PM this week in a leaked letter urging her not to soften Brexit .

The 62 MPs from the European Research Group demanded "full regulatory autonomy" after Britain leaves the EU.