Lord Lisvane has issued a complaint against former House of Commons speaker John Bercow this week.
Lord Lisvane is a former senior adviser to the ex-speaker after serving as Clerk of the House between 2011 and 2014, when Bercow was in post.
He held a number of procedural roles after he first began working at the Commons in 1972, and was made a crossbench life peer after stepping down as Clerk of the House in 2014.
Lord Lisvane confirmed that he had lodged the complaint with the Parliamentary Commissioner for Standards on Wednesday, the nature of which is believed to concern bullying allegations against Bercow.
Bercow stood down as Commons speaker last year and said that Lord Lisvane had "at no stage" ever raised such issues with him during his time as Clerk of the House, despite having "ample opportunity" to do so.
Bercow said: "At no stage did he do so, even though he became Clerk of the House - the most senior official. The timing of this intervention is curious.”
It has been recently reported that Bercow has been nominated for a peerage of his own by Labour leader Jeremy Corbyn.
Bercow, who served as speaker for ten years, has faced numerous accusations of bullying during his term and denied all claims.