The broadside came from the Facebook account of Darien Fenton, a Labour MP from 2005 to 2014, and was sent via a private message. Sharma posted screenshots of the messages and posted them in replies to his own Facebook page.
The messages related to Sharma's decision to publish a column in The New Zealand Herald in which he alleged there was an environment of bullying at Parliament, including within his own party.
Sharma took aim at Parliamentary Service, the party whips' offices and leaders, saying bullying was "rampant".
"Where concerns have been raised with Parliamentary Service about staff or MP colleagues showing unacceptable behaviours, in some cases there does not appear to have ever been any investigation or an intent to investigate," he wrote.
In the message, Fenton said Sharma should have spoken with the public service union before going public.
"You should have talked with the PSA [Public Service Association] before you went off in the media about Parliamentary Services et al. I am appalled by you [SIC] ill discipline in mouthing off in the media (current PSA organiser and former Labour MP)," Fenton wrote.
"Seems like you are still on the party payroll?" Sharma replied.
"Mind your own business," he said.
Sharma then rebuffed Fenton's criticism of not using appropriate channels to raise concerns, saying he had "made multiple complaints including to the PMO [Prime Minister's Office] over the last 1.5 years and nothing has been done".
Sharma has only been an MP since the 2020 election. This timeframe would mean he began complaining to the Prime Minister's Office about half a year after entering Parliament.
"What's appalling is that despite being a former MP and a union representative you want to victimise me instead of asking the party what they did about the bully."
"Have a hard look at yourself in the mirror. You are the reason bullying is still a problem," Sharma wrote.
On Thursday night, Parliamentary Service and Labour's chief whip Duncan Webb referred to an employment matter concerning Sharma.
Parliamentary Service chief executive Rafael Gonzalez-Montero revealed they had been working through "employment matters" involving Sharma.
"The Parliamentary Service works alongside whips from all parties," he said.
"This has included working closely with the Labour whip's office over the past year to address employment matters with Dr Sharma.
"We do what we can to support all our MPs, and we acknowledge the triangular employment relationship at Parliament is complex.
"It is also important to make it clear that the service cannot direct MPs what to do and how to act.
"MPs are elected representatives of New Zealand's citizens as that would impinge on New Zealand's democracy, and the free right of MPs as elected representatives of New Zealand's citizens."
Webb also said they'd been working with Parliamentary Services to address employment matters in Sharma's office.
"We had been working to provide support for Gaurav and find a solution. We're committed to reaching an outcome everyone is happy with."
Speaker Trevor Mallard said he would not discuss individual MPs or staff relationships.
"A practice was developed during the last Parliament and has continued into this Parliament where MPs who have ongoing staff relationship issues have been delayed in their appointment of new staff until the whips and Parliamentary Service are convinced they have sufficient skills to properly supervise them."
Fenton declined to comment. Sharma was approached for comment.
