Boris Johnson has seemingly mocked Theresa May over Cabinet Brexit divisions – just minutes after the Prime Minster faced a grilling over splits in her top team.

Speaking in the Commons after Prime Minister’s Questions, the Foreign Secretary quipped he was in “conformity” with Theresa May over the UK’s post-Brexit customs policy – as the policy has “yet to be decided”.

The remark, which left many on the Tory benches seemingly stunned, was delivered as Johnson was making a statement on President Trump’s decision to pull out of the Iran nuclear deal.

Johnson’s claim came just 45 minutes after May was forced to defend her Foreign Secretary after he described her preferred customs partnership plan as “crazy” in an interview on Tuesday – a move which pushed Cabinet tensions over the UK’s Brexit policy out into the open.

Answering a question from Tory veteran Ken Clarke, in which Johnson was praised for his “unswerving loyalty to collective Government policy” during his statement on Iran, Johnson said: “I’m completely in conformity with Government policy on the matter I believe he is referring, since that policy has yet to be decided.”

Fellow Foreign Office Minister Harriet Baldwin, who had been laughing moments earlier as Johnson joked about Clarke’s own loyalty, seemed to deliberately not react to the remark.

Other ministers on the frontbench, including the Foreign Office’s Alastair Burt and Defence Minster Tobias Ellwood, also appeared less than impressed. 

The jab over the lack of agreement on the UK’s post-Brexit customs policy came after Labour leader Jeremy Corbyn quizzed May over the stalemate among her top team.

Speaking in Prime Minister’s Questions, Corbyn claimed May has had “23 months in order to negotiate an agreement and hasn’t made any progress on it.”

He also asked whether she agreed with Johnson that a customs partnership was “crazy.”

May replied: “We are leaving the European Union, we are leaving the customs union, but of course for our future trade relationship with the European Union we will need to agree customs arrangements which will ensure that we leave the customs union, that we can have an independent free trade policy, that we can maintain no hard border between Northern Ireland and Ireland and that we have as frictionless trade with the European Union as possible.”

She also accused the Labour leader of being in opposition to the majority of Brits by wanting to keep the UK in a customs union with the EU.