John Bercow has accused Downing Street of trying to scupper his chances of being made a peer, and dismissed accusations of bullying made by his former most senior official.

Amid an escalating and increasingly public row with No 10, Bercow said 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”.

He 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.”

Asked why Downing Street had ignored the convention that Speakers are elevated to the Lords after they step down, a No 10 source said: “The Speaker was not always a fan of convention.”

The comments came after Downing Street called the new allegations of bullying against Bercow “very concerning”, adding further doubt to the reported push by Labour to make him a peer.

A No 10 spokesman declined to comment specifically about allegations made to the parliamentary commissioner for standards accusing Bercow of having bullied and humiliated staff, which the former Speaker has vehemently rejected. But the spokesman said any such claims should be fully investigated, adding that any appointments to the Lords must first be vetted by an independent commission “for propriety”.

It is understood that Robert Rogers, who was clerk of the Commons for three years during Bercow’s tenure before becoming a crossbench peer in 2014 as Lord Lisvane, has filed a formal complaint about the former Speaker to the parliamentary commissioner for standards.

Former Speakers are traditionally made peers, but Boris Johnson’s government is resistant to elevating Bercow, in part due to bullying claims but also because of his role in helping MPs better scrutinise and amend the Brexit process.

Jeremy Corbyn has instead reportedly included Bercow among the Labour party’s peer nominations for the honours list marking the dissolution of the last parliament, which is due soon.

According to the Times, which first reported the allegations, Rogers said Bercow bullied and humiliated staff, including by using inappropriate language.

The No 10 spokesman said: “These are very concerning allegations and they need to be investigated thoroughly. Everyone working in parliament deserves to be treated with dignity and respect. 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 that are raised.”

The spokesman said he had “no knowledge” of any nominations for peers, and could not comment on Bercow’s case: “All nominations are subject to independent vetting by the House of Lords appointments commission for propriety before their appointment.”

Bercow said in a statement: “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.”

He said the former Commons clerk had “ample opportunity to raise any concerns about such conduct with me” and had “a duty of care to all house staff”. “Therefore, he had not merely a right but a responsibility to act if he thought that he witnessed misconduct,” Bercow said.

“The simple fact is that he did not at any time do so. Even though he frequently disagreed with me on a wide range of issues, he did not once complain to me and neither did any other official on his behalf.”

The business secretary, Andrea Leadsom, a former leader of the Commons, has said that if the complaint of bullying is upheld, it should have an impact on whether Bercow is made a peer.

Leadsom said the complaints procedures for Commons staff that she helped to establish applied to everyone in the house.

“The whole purpose of that was that anybody, including the Speaker of the House of Commons, whoever he or she may be, should also be subject to that procedure,” she told Sky News. “In the event that there are genuine, upheld complaints about any persons, that should have an impact on whether they are found suitable for the House of Lords.”

Bercow left the Speaker’s chair on 31 October and was succeeded by Sir Lindsay Hoyle.