Boris Johnson has accused Sir Vince Cable of "peddling lies" about him after the Liberal Democrat leader made reference to rumours the Foreign Secretary may be about to resign.

The heated response came after Sir Vince seized on apparent differences between International Trade Secretary Liam Fox and Chancellor Philip Hammond over plans for a post-Brexit three year transition period for migrant workers in order to brand the Cabinet as being in a state of "civil war".

The Lib Dem leader added: "There is no Cabinet consensus for moderation. And the rumours of Boris Johnson being about to resign fuel the uncertainty."

Responding to the claims, a spokesman for Mr Johnson said: "Vince Cable is making his stuff up and maybe he should take more time to think up some policies rather than wasting his time on peddling lies.

"Boris and Philip Hammond are working closely to take the the UK out of the EU and are not going to be diverted from that important task."

The war of words erupted after Dr Fox insisted unregulated free movement of labour after Brexit would "not keep faith" with the EU referendum result.

Dr Fox insisted the Cabinet has not agreed a deal on immigration after withdrawal from the EU.

This appeared at odds with Mr Hammond's signal that free movement would continue for a limited period in all but name with an added element of migrants having to register in the UK.

Mr Johnson has yet to comment publicly on Mr Hammond's transitional plans.

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Sir Vince hit back.

"If the Foreign Secretary is working so closely with the Chancellor, can he confirm that he supports the Chancellor's call for a three-year transitional deal with continued free movement of labour? So far he has been uncharacteristically silent on the subject," he said.

"It is a simple question: does he support the position of Philip Hammond or Liam Fox? Because he can't support both.

"And if Philip Hammond secures a three year transitional deal, can Boris Johnson confirm he will stay in the Government and support the policy?

"I have a policy: it is to stay in the single market and customs union to protect British jobs and living standards."