Matt Hancock has been forced to apologise after parliament’s sleaze watchdog found he broke House of Commons rules by trying to lobby an official investigating another Conservative MP for lobbying. The former health secretary, who sits as an independent, having been stripped of the Tory whip, was found to have committed only a “mild” breach of the rules. However, Hancock was given a rap on the knuckles for a “lack of attention” to the MPs’ code of conduct. An update endorsed by MPs in December 2022 makes “lobbying the commissioner in a manner calculated or intended to influence his consideration” a specific offence. Hancock had written to Daniel Greenberg, the Commons standards commissioner, about an ongoing inquiry into the former health minister Steve Brine. The intervention was unsolicited, and came after messages between Brine and the cabinet minister Michael Gove were published as part of a leaked cache of WhatsApps. The messages revealed that Brine had been trying “for months” to “help the NHS” by connecting it with a company called Remedium. It is a recruitment firm offering doctors for free to the health service, for which he was a paid strategic adviser. Hancock’s actions on 28 March “sought to influence” Greenberg’s inquiry into Brine, the commissioner said. He did not ask the commissioner in advance if the letter would be helpful or check if the terms of reference into the Brine investigation meant it would assist. “The lobbying in his letter was likely due to inattention and carelessness rather than a deliberate attempt to subvert the commissioner’s inquiry into Mr Brine,” a new report on Hancock’s behaviour said. Hancock may have broken another rule, the commissioner said, after his spokesperson issued a public statement about the matter – in direct contravention of a ban on MPs commenting on live investigations. Greenberg said it did not hinder the inquiry, so decided against imposing any sanction, but added that it underlined a “further lack of attention” to the rules. Hancock maintains his innocence. Speaking in the Commons on Monday, the West Suffolk MP said he accepted the watchdog’s findings but wrote to Greenberg only to “give context to an investigation he was leading”. Hancock said he was happy to reiterate his “respect for the code [of conduct] and the processes of investigating potential breaches of the code”. He said he was “happy” to apologise. Hancock’s experience was viewed as an aggravating factor, given he has been an MP for 13 years. The standards committee, which is made up of MPs and lay members and scrutinises decisions by the commissioner, said it was “concerning that a member with this experience has not taken account of these provisions of the code”. However, leniency was given to Hancock because the committee said he did not mean to break the rules, and had no prospect of personal gain through writing the letter. Hancock will also be required to attend a briefing on his obligations under the rules. Brine was found by Greenberg last month to have not properly declared his second job for Remedium Partners but cleared of paid advocacy because his efforts were not seeking “financial or material benefit” for Remedium because the doctors’ services were offered pro bono.