World leaders and ambassadors rarely quiz Boris Johnson about the UK's historic decision to leave the EU, according to British foreign secretary.

The top Conservative told a group of MPs that he was "stuck" by how little the Brexit issue is raised with him during his travels abroad.

Johnson made the claim as he appeared before the powerful Foreign Affairs Committee on Thursday morning (13 October).

The cabinet minister, the chief cheerleader of the Vote Leave campaign, also argued it was "fiction" to say the EU would not budge on its free movement of people rules.

"The idea that the Brownian motion of citizens across EU is set in tablets of stone in Brussels is absolute nonsense," Johnson said.

The Foreign Secretary had previously branded assertions from the EU that the UK could not have "single market a la carte" – immigration curbs and extensive access to the trade bloc – as "complete baloney".

He also stressed that he saw no contradiction between "taking back control" from the EU and promoting a "Global Britain", a slogan Theresa May's government have adopted. "We are leaving the EU, not leaving Europe," Johnson said.

He promised the UK government would not be "hostile to people of talent", in the wake of the Conservative administration's U-turn over a now-aborted plan to make businesses list the number of foreign workers they employ.

Johnson said the UK's decision to leave the EU should be seen as "positive thing", while branding the EU's single market as ""increasingly useless". Liberal Democrat leader Tim Farron described Johnson's performance as "bungling".

"It's clear the only thing which is becoming 'increasingly useless' is Johnson himself," Farron said. "His glib dismissal of the single market shows the Conservatives have given up any claim to be the party of business and are putting jobs, prosperity and lower prices at risk.

"The Liberal Democrats are the real voice of opposition to this Conservative Brexit government, and will fight to keep Britain open, tolerant and united."

The government has promised to trigger Article 50, the official mechanism to split from the EU, by March 2017. But they face a legal challenge in England's High Court over the move from today, with a call for parliament to have a say on the process and negotiations with the EU.