An MP was greeted with laughter from the Government benches after she asked when Theresa May would fulfil Boris Johnson's Brexit pledge of £350m for the NHS—and accused the Foreign Secretary of "smirking at the British public".

Labour's Tulip Siddiq asked whether the Prime Minister would honour the Vote Leave campaign slogan used by prominent Brexiteers including Mr Johnson and Michael Gove, and which was plastered across the now-infamous red bus.

Cabinet minister Chris Grayling later claimed the slogan was merely an "aspiration".

Speaking during Prime Minister's Questions, Ms Siddiq said: "The Foreign Secretary during the EU referendum campaign urged people to, and I quote, 'Take back control of huge sums of money, £350m a week, and spend it on our priorities such as the NHS'.

"The Prime Minister will trigger Article 50 today. Can the Prime Minister confirm precisely when she wants to fulfil the promise made by her cabinet colleague, who is sitting on the front bench smirking at the British public?"

Commons speaker John Bercow was forced to step in to restore order after disruption from both sides of the House, noting of Mr Johnson that there was "an air of repose about the fellow".

Ms May said: "Of course, when this country leaves the European Union we will have control of our budgets, and we will decide how that money is spent."

Mr Johnson has previously been ambushed with a giant £350m cheque and asked to sign it in order to fulfil the pledge.

But he refused, and told Sky News reporter Darren McCaffrey it was "because you’re doing a pointless stunt".

Ms Siddiq's question came on the day the UK Government sent its Article 50 notification to Brussels, beginning the two-year process of divorce from the EU.