Commons Speaker John Bercow insists his impartiality has not been affected after he revealed he had voted Remain in the EU referendum.
The Sunday Telegraph reported that he had spoken about his voting stance to students at Reading University.
A spokeswoman for the Speaker, expected to be politically neutral, said his vote against Brexit did not affect his ability to handle MPs’ debates fairly.
Labour deputy leader Tom Watson called Mr Bercow “one of the great Speakers”.
Mr Bercow is already facing calls for him to be replaced for voicing his opposition earlier this week to US President Donald Trump addressing Parliament on his UK state visit.
But Leader of the House of Commons David Lidington told BBC One’s Andrew Marr Show that his future was a “matter for members of the House” as a whole, saying it was “really important… that the government doesn’t get involved” in saying who should be Speaker.
‘Big power bloc’
Talking to Reading students on 3 February, Mr Bercow said: “Personally, I voted to remain. I thought it was better to stay in the European Union than not.”
He said this was “partly for economic reasons – being part of a big trade bloc – and partly because I think we’re in a world of power blocs.
“I think for all the weaknesses and deficiencies of the European Union, it’s better to be part of that big power bloc in the world than thinking you can act as effectively on your own.”
He also said immigration was a good thing and expressed concern Labour had not done more to strike a “very clear, resonant Remain note”.
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Mr Bercow’s spokeswoman said he had voted in last June’s referendum “along with millions of others”.
“The record shows that he has rigorously facilitated the raising of concerns of those on both sides of this argument, as he does on every other issue,” she 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.
“He is required to be politically impartial in his conduct in the chair, irrespective of any private views he may or may not hold on the matters before the House, and ensure that those matters are given a fair and transparent scrutiny, and he has absolutely done this.”
But Conservative MP James Duddridge, who has tabled a motion of no confidence in the speaker over his Trump comments, told the Telegraph Mr Bercow could not continue after expressing views on Brexit.
The parliamentary website states: “The Speaker is the chief officer and highest authority of the House of Commons and must remain politically impartial at all times.
“On election the new speaker must resign from their political party and remain separate from political issues even in retirement.”
Mr Lidington told the Andrew Marr Show that when he had served as Europe minister, Mr Bercow had not been “shy of calling” those “hostile” to the UK’s membership of the EU to speak in the Commons.
He said the Speaker “has his very strong supporters and his critics in the House of Commons”, but had to have “the confidence of the Commons as a whole”.
‘Honest and honourable’
On the same programme, Mr Watson said Mr Bercow “absolutely” had the backing of MPs, adding: “He’s one of the great Speakers the House of Commons has known. He gives backbenchers their voice.”
On ITV’s Peston on Sunday, former Culture Secretary John Whittingdale, a prominent Brexit campaigner, said he was “a bit surprised” Mr Bercow had voted to stay in the EU, adding: “We had been told privately that he was sympathetic to our cause.”
Mr Bercow, who became Speaker in 2009, was “coming to the end of his time, in any case”, he added.
Earlier this week Mr Bercow, who was a Conservative MP before being elected speaker, defended his opposition to Mr Trump addressing Parliament.
His comments, including accusing the US president of “racism and sexism”, had been made “honestly and honourably” and were within his remit, he told MPs.
Several Conservatives have criticised the Speaker, with one saying his career could be in “jeopardy” and another that he had damaged the national interest.
Downing Street called his comments “a matter for Parliament”.