The shadow cabinet minister leading Labour’s response to the Westminster bullying scandal has herself been spoken to by her party leadership after a bullying complaint, the New Statesman has learned.

Valerie Vaz, the shadow leader of the House of Commons, was met by Jeremy Corbyn’s office and that of Nick Brown, the Labour chief whip, after a former member of her Westminster staff complained that they had been subject to workplace bullying while employed by Vaz in 2012. She denies the allegations.

The New Statesman understands that the complainant also contacted Laura Cox's inquiry into bullying and harassment in parliament to raise the same concerns. Vaz led Labour's response to an urgent question on the report on Tuesday.

In a letter to the complainant in August, seen by the NS, Labour said it would not pursue any formal investigation or disciplinary action against Vaz on the grounds that its historical nature would make it difficult to judge fairly.

The party’s Head of Complaints wrote: “The Labour Party has not codified a strict time limit on historic investigations but we have considered your case and believe the passage of time means it will be difficult to conclude a case fairly. Therefore we will not be taking formal disciplinary action.”

She added: "Valerie Vaz has been met by [the] Leader’s Office and the Chief Whip’s Office following your complaint, to be reminded of her requirements as an employer under the Labour Party Code of Conduct.

“It has been decided in this case that there will not be an investigation into the complaint and no further action taken. The option of complaint via the Parliamentary Commissioner for Standards remains an option to you.”

While the Standards Commissioner is able to investigate complaints dating back seven years, the process is ultimately overseen by the MPs on the Commons Committee on Standards.

Parliament’s new independent complaints and grievances procedure, introduced in July, has no MP oversight but cannot investigate claims that date to before the start of the 2017 parliament. Vaz left the cross-party group that oversaw its development in January 2018.

In her report on bullying and harassment in parliament, released on Monday, Cox recommended that the new grievance procedures be given the power to investigate historical allegations.

Labour responded to the complaint against Vaz before that recommendation was made, noting: “The ICGP agreed by the House of Commons in July 2018 selected “the start of this Parliament for the retrospective application of investigations under the Scheme” on the advice of Tom Linden QC that “an investigation of a complaint will be more difficult the further into the past you go.”

However, in the event that Cox’s recommendation was adopted, the complaint against Vaz would be admissible under the new procedure. Asked about the report today, a spokesman for Jeremy Corbyn said Labour was pushing for the issue of historical allegations to be "properly addressed".

Vaz has avoided explicitly endorsing the recommendations made in Cox’s report and has instead promised to “look seriously” at their detail. Responding after its publication on Monday, she said: “Sexual harassment and bullying must not be tolerated in any workplace. Some of the accounts in this report are truly shocking.

“The House of Commons has recently passed an independent complaints process to deal with cases of bullying, sexual harassment and victimisation under the supervision of the Parliamentary Commissioner for Standards.

“Labour thanks Dame Laura Cox QC DBE for her report and will look seriously at the detail of the recommendations. We will continue to work on a cross-party basis to tackle this and ensure new procedures are as robust and effective as possible in order to protect everyone working in and visiting the House of Commons.”

A spokesperson for Vaz said: “Valerie vigorously denies these allegations, which are vindictive and defamatory, and is committed to tackling bullying and harassment in Westminster, which has gone unchallenged for too long.”

A Labour Party spokesperson said: "The Labour Party takes all complaints of bullying extremely seriously, and we insisted that new complaints processes in Parliament fully cover bullying as well as harassment and sexual misconduct.

"We are pleased these processes are now in place and we will continue to bring forward proposals to ensure they as robust as possible. The Labour Party's complaints procedures are confidential so we cannot comment on individual complaints."