The House of Commons Speaker, John Bercow, has sparked a fresh row among British MPs after he admitted voting to stay in the European Union in the June 2016 referendum.

It is parliamentary convention for the Speaker of the House to remain impartial regarding political matters, despite being an MP, as the role involves chairing debates between MPs and occasionally disciplining them.

Bercow is already facing a vote of no confidence after effectively banning the US President Donald Trump from speaking to the Houses of Parliament during a state visit later this year.

Now, it has emerged he may have breached parliamentary rules while discussing the European Union with students from the University of Reading.

In a talk to the students, Bercow said: "Personally, I voted to remain. I thought it was better to stay in the European Union that not, partly for economic reasons: being part of a big trade bloc and partly because I think we're in a world of power blocs.

"And I think for all the deficiencies and weaknesses of the European Union, it's better to be in that big power bloc in the world than thinking you can act as effectively on your own, under a lot of supranational and multilateral and global challenges, which I think we're better placed to tackle as part of a wider group and so I voted to remain.

"The public voted for Brexit… the result is what the result was and I think parliament will give effect to the result of the referendum.

"Now, there is an argument to be had about what form that Brexit takes but do I think it will happen? I do. Of course, parliament could have a second referendum but there's no sign of that at the moment and I'm not complaining about the result. I'm saying to honestly, I voted to remain, but the public have decided otherwise."

The video was filmed on 3 February but was not published on the university's YouTube channel until 9 February.

Some MPs have said that Bercow's position as Speaker is untenable now that he has expressed his views on Brexit, given that it will be the subject of debate for weeks to come.

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The UK parliament's website says that the "Speaker is the chief officer and highest authority of the House of Commons and must remain politically impartial at all times… therefore, on election the new Speaker must resign from their political party and remain separate from political issues even in retirement".

James Duddridge, Conservative MP for Rochford and Southend East, told the Telegraph: "Speaker Bercow cannot come back to the chair having expressed views on Brexit. He is incapable of chairing parliament as Speaker on any European business."

However, David Lidington, Conservative MP for Aylesbury and the Leader of the House of Commons – the cabinet position for arranging the government's business in the House of Commons – stood by Bercow.

Appearing on the BBC's The Andrew Marr Show on Sunday (12 February), he said: "I think had this been before the referendum then yes, I would have had concerns.

"I mean, he said what he said. Every member of parliament is responsible for what they say. What I can say is that I had more than six years as Europe minister under David Cameron and in that time, I never found the Speaker was shy of calling on lots of people who were critical of the EU to ask me difficult questions."

A spokesman for Bercow insisted he had been even-handed when chairing debates.

He said: "The Speaker's impartiality is required on matters of debate before the House, and he has been scrupulous in ensuring that both sides of the argument are always heard. Furthermore, his comments made clear that he absolutely respected the result of the referendum."

Bercow's spokesman added: "How he voted and whether or not he said how he voted after the event is completely irrelevant. It had absolutely no bearing on his impartiality."