Downing Street has said that any complaints of bullying in Parliament should be "fully investigated", following allegations of abuse of staff by MPs including Speaker John Bercow.
An investigation by BBC's Newsnight claimed female clerks working for the Commons faced harassment or bullying and suggested that their careers suffered if they complained.
Mr Bercow denied bullying behaviour, while a House of Commons spokesman said it was a "responsible and supportive employer" and did not tolerate "bullying or harassment of any kind".
But a Downing Street spokesman said that Prime Minister Theresa May regarded the allegations as "concerning".
"The Prime Minister is clear that there can be no place for bullying or harassment of any kind at Westminster, and everybody should be free to work in an environment that is safe and respectful," said the Number 10 spokesman.
"If any complaints are made, they should be fully investigated."
He added: "With regard to the Speaker, I note the allegations are being contested, but I think these are concerning allegations and there can be no place for bullying or harassment of any kind. If complaints are made, they need to be investigated."
Asked whether Mrs May had confidence in Mr Bercow as Speaker, the spokesman said: "Yes."
Newsnight conducted dozens of interviews and reviewed internal parliamentary human resources documents as part of its investigation.
The BBC programme claimed Bercow had a reputation as a bully, highlighting Kate Emms' short-lived tenure as his private secretary from May 2010 to February 2011.
The programme claimed she was undermined by Bercow and he appeared to frequently shout at her.
The Speaker's spokesman said: "The Speaker completely and utterly refutes the allegation that he behaved in such a manner, either eight years ago, or at any other time. Any suggestion to the contrary is simply untrue."
Allegations were also made about Tory MP Mark Pritchard and Labour's Paul Farrelly.
Clerks told the programme that Wrekin MP Pritchard was "particularly nasty to those he felt were below him" and was "known for having a dreadful temper".
He allegedly swore at an official, telling her "you haven't got a f***ing clue what you're talking about".
Pritchard told the programme: "I understand, over the past several years the House authorities have addressed numerous complaints about MPs, but they have also informed me they have no record of any complaints against me, and if they had, I would have been notified."
Farrelly, a member of the Culture, Media and Sport Select Committee, was the subject of a formal complaint under the House's Respect policy in 2012 in relation to his treatment of clerk Emily Commander, the programme said.
The inquiry conducted by House official Edward Wood concluded there had been "an abuse of power or position, unfair treatment and undermining a competent worker by constant criticism", adding "the conduct was offensive and insulting".
But the House of Commons Commission, a panel of MPs chaired by the Speaker, could not reach a decision on what to do, Newsnight said.
Mr Farrelly told Newsnight: "In 2012 allegations were made about me having bullied a clerk to the Committee during the compilation of the phone hacking report.
"These allegations were investigated and not upheld.
"Despite this, I apologised if I had inadvertently upset the clerk who had suffered stress.
"The policy under which they were investigated was considered to be so unfair to those complained about that it was immediately withdrawn and replaced by another policy."
A House of Commons spokesman said: "We take the welfare of our staff extremely seriously, and strongly reject any claims to the contrary.
"It is a grotesque exaggeration to suggest that members of the House of Commons service work in a 'culture of fear' in relation to dealing with bullying and harassment by MPs.
"The House of Commons takes pride in being a responsible and supportive employer and does not tolerate bullying or harassment of any kind."
A cross-party panel convened by May put forward proposals last month for an independent complaints and grievance system for MPs' staff, but this is not currently planned to cover employees of the Commons and Lords, such as clerks.
The Number 10 spokesman said: "The Prime Minister led the drive to secure cross-party agreement on establishing an independent complaints and grievance policy which will explicitly deal with complaints of bullying as well as sexual harassment. The aim is for further work to be undertaken so that employees of the two Houses are included in these new arrangements."