Labour MP Iain Lees-Galloway has shared an abusive email sent to him by a member of the public opposed to the Government's beefing-up of union rights.
The email begins, "You and your party are full of shit," and goes on to call the Minister for Workplace Relations "f**king dumb" and "just f**king nuts".
"Any union organiser that walks on this premises I will order them off the property and they can f**k off," the email, shared on Twitter, states.
"We will sack the staff and close the business... I have already warned both my admin people in my small business x2 they know I will dismiss them and employ my wife to run that if you implement this."
The author claimed to be involved with three companies.
Mr Lees-Galloway suggested the person has a lot to learn.
"I bet this guy is a delight to work for. Pro tip: Making personal threats is not a great lobbying strategy," he tweeted.
Labour's changes include doing away with employment law changes introduced by the previous National Government, largely concerning union rights and collective bargaining, as well as taking 90-day trials away from businesses with 20 or more employees.
Mr Galloway said he has referred the email and its sender to the Diplomatic Protection Service.