The statement comes after his former Clerk of the House, Lord Lisvane, made a formal complaint about him to the Parliamentary Commissioner for Standards.

But Mr Bercow said he had never "bullied anyone, anywhere at any time".

The former Speaker also criticised the government for failing to nominate him for a peerage.

He said that, since retiring, it had "become increasingly obvious that the government has no intention of honouring the centuries-old convention that a departing Speaker is promptly elevated to the House of Lords".

Mr Bercow added: "Indeed, it has been suggested to me that the government actively seeks to block any other attempt to nominate me for membership of the upper House."

There have been reports that the former Speaker - who previously sat as a Conservative MP - has been nominated for a peerage by the outgoing Labour leader Jeremy Corbyn.

But Downing Street said appointments to the House of Lords are "a matter for house authorities" and they were "not aware of a nomination being put forward".

A No 10 source suggested to the BBC that Mr Bercow's accusation showed a lack of understanding of the process of nominations for a peerage, adding: "The speaker wasn't always a fan of convention."

Lord Lisvane, who served as Clerk of the House between 2011 and 2014, confirmed to the BBC he had submitted a formal complaint on Wednesday, which was understood to be centred around bullying.

In an earlier statement, Mr Bercow - who stood down in 2019 after 10 years in the chair - said his former colleague had "ample opportunity" to raise issues in their time working together, adding that the timing of the intervention was "curious".

On Thursday afternoon, he said: "I have seen in the media that Lord Lisvane is formally complaining that I bullied staff.

"For the record, I categorically deny that I have ever bullied anyone, anywhere at any time."

Mr Bercow has faced other accusations of bullying during his time in office, but has denied all the claims.

'No place for bullying'

No 10 said the allegations were "very concerning" and should be "investigated thoroughly".

The prime minister's spokesman added: "There can be no place for bullying or abuse in Westminster or any workplace, and it is important that the parliamentary leadership responds fully and promptly to any concerns which are raised."

Lord Lisvane began working at the House of Commons in 1972 and has held a number of procedural roles, including clerk for Private Members' Bills and clerk for the European Scrutiny Committee.

He became Clerk Assistant and Director General of the Chamber and Committee Services in 2009, before stepping up to the Clerk of the House of Commons in 2011.

After standing down in 2014, he became a life peer and sits in the House of Lords as a crossbencher.

'Taken into account'

Earlier, former Leader of the Commons Andrea Leadsom said anyone found to have bullied or harassed colleagues in Parliament "should not be offered a peerage".

The now-business secretary, who clashed with Mr Bercow on a number of occasions in the Commons, told BBC Radio 5 Live: "I worked cross-party to put in place a complaints procedure which would mean anybody, whoever they are, including the Speaker of the House of Commons, or indeed of the Lords, would be subject to those same complaints procedures.

"Specifically, we made sure if you were an MP and you were potentially going to be offered a peerage, that anything that was alleged against you would be taken into account.

"So, I think it is really important, whoever you are, that all of those complaints are taken seriously."