The spat began on Monday evening when Mr Beattie dismissed a tweet from TUV leader Jim Allister as “nonsense”.
Mr Allister had posted the text of an Assembly question – asking the health minister “what precautions are in place to prevent citizens of the Republic of Ireland from availing of free COVID-19 testing kits and facilities in Northern Ireland; and how extensive this has been in border areas?”
Mr Beattie replied: “I simply cannot understand this nonsense. I’d happily share with my neighbour, the same neighbour who sent ambulances & crews to help us fight COVID…. or put up helicopters to help us fight bush fires.”
The reply prompted Mr Girvin, who is the TUV’s 2022 Assembly election candidate for South Belfast, to tweet: “I don’t think so Doug. I pay my taxes for those from here to avail of, not those from a totally different country who have their own health service, government, taxes, economy and currency. Stick to drinking beer and taking pics of your belly.”
Mr Beattie hit back by saying: “You really are an oxygen thief.”
The row continued on Tuesday morning with a number of Twitter users suggesting the UUP leader had overstepped the mark.
One said: “Thought you’re meant to be inclusive, mental health champion, cuddly political icon or was that propaganda for the Belfast Telegraph?”
Another said: “Being a public figure you think you’d have thicker skin... not a great look for a politician basically telling potential voters that they’re an oxygen thief”.
A number of other Twitter users spoke out in support of Mr Beattie, including one who said: “Oh look, Andy is playing the victim! You can dish it out and can’t take it, eh? Grow up.”
The TUV advice service in Belfast has called on Mr Beattie to apologise for his comment at a “time when there is so much vile abuse on Twitter,” saying it is “surely not acceptable for the leader of a political party to decide someone would be better off dead”.
However, speaking to the News Letter, the Upper Bann MLA and former army officer said he was always going to “bite back” if insulted.
“If a TUV councillor attempts to insult me then he must expect to have a bite back,” Mr Beattie said.
“He was bitten back and he doesn’t like it. What I would suggest to these people is if they want to play big boys games, or childish games, then I am more than happy to drop to their level.”
Mr Beattie also rejected the suggestion that the term ‘oxygen thief’ is particularly sinister.
“If they look up what that term means, it does not mean what they suggest it means.”