A Queen's university virologist has described as "gross misinformation" a DUP councillor's claims the new Covid-19 vaccine contained "stem cells and tissue from aborted babies".
Asked about the comments, the DUP urged everyone to take the vaccine.
The Pfizer-BioNTech vaccine, which was rolled out early this week, is made entirely from synthetic material and has no biological element.
Mid and East Antrim councillor John Carson said on Facebook he would definitely not take the treatment.
And in a Stormont press conference on Thursday, First Minister Arlene Foster would not be drawn on whether the councillor would face internal disciplinary procedures but said his comments were 'wrong'.
"The position I have and that the party has is this vaccine is safe and people should take it.
"In terms of the internal discipline, those matters will be dealt with internally, but John's wrong and he should reflect on that because some of the things he's said are palpably not true."
A spokesperson for the Department of Health dismissed his comments and stressed the need for the public to take the vaccine in order to protect and save lives.
"The Pfizer vaccine does not contain any human tissue," they said.
"It should be remembered that vaccines have saved millions of lives worldwide.
"We need widespread take-up of the Covid-19 vaccine in NI to protect the population, particularly older and vulnerable citizens.
"Widespread take-up will also help us move towards the easing of restrictions in society."
When asked by a Facebook user on December 7 whether he would be taking the vaccine, Mr Carson replied "Definitely no!!!" before making his erroneous claims.
Health Minister Robin Swann asked on Thursday for people objecting to Covid-19 vaccination on anti-abortion grounds to think again.
"It is disappointing that people calling themselves pro-life would be objecting to vaccination programme that will save many lives."
"It is the case that the development and testing of some vaccines can include the use of human cell lines grown in labs, having been replicated from fetal cells obtained in previous decades following abortions.
"If people want to object on those grounds and leave themselves unprotected from Covid-19 that is their choice. They will be at odds with other pro-life advocates including the Irish Catholic Bishops’ Conference who issued a very clear statement this week.
"Any link between any vaccination development and abortions is incidental and remote, involving cells replicated in labs."
In a statement, a DUP spokesperson said: "Everyone who is recommended to take the Covid-19 vaccine should do so in order to protect themselves and others in our community."
Mr Carson did not return calls from the Belfast Telegraph.
Speaking to BBC Radio Ulster's Nolan programme, Professor of Molecular Virology at the Wellcome-Wolfson Institute for Experimental Medicine Ultan Power labelled the claims "gross misinformation".
He said he "absolutely and categorically confirms" stems cells and foetal tissue from aborted babies is not used to make the vaccine.
"The Pfizer vaccine is a synthetic vaccine made by chemistry rather than biology. It's not derived from any cells, not to mention cells originally derived from fetuses and stem cells."
He said the vaccine was"critical" and will be "the means by which we get to control and get on top of the virus and basically put this pandemic behind us".
On Wednesday, UK regulators issued a warning that people who have a history of "significant" allergic reactions should not currently receive the Pfizer/BioNTech Covid-19 vaccine.
That came after two NHS nurses who had the jab via the mass vaccination programme on Tuesday had allergic reactions.
Professor Power said the trials carried out before the vaccine was approved, although a large number took part, were small compared to the number who will eventually receive the vaccine.
"When you get 20,000 people or thereabouts who receive the vaccine, that's obviously a very large trial, but compared to the number of people who will receive it in society, it's only a very small fraction.
"It's the obligation of the MHRA to follow very closely and monitor any serious and adverse reactions following the rollout of the vaccinations.
"Now the recommendations have been updated accordingly to reflect the data that has been generated since," he said.
The virologist said a substance used to generate the Oxford vaccine was originally developed using aborted foetus but said this was no longer the case.
"There is a cell line that's being used to generate the Oxford vaccine which is called HEK293 cells. These were originally developed in the 1970s from aborted foetus. But that no longer bears any resemblance to human tissue at this stage. It's just not possible," he said.
"The idea that there are human stem cells and human aborted foetal tissue being used to produce the vaccines is gross misinformation. There's no direct use of any human tissue for any vaccine manufacturing process, it just wouldn't be allowed."
In April, Councillor Carson caused controversy for claiming the pandemic was God's judgement for abortion law reforms and legalising same-sex marriage in Northern Ireland.
He later said his online remarks were "misinterpreted" and he did not intend to cause hurt or offence, but added: "I will never apologise for my Christian faith."
At that time the DUP distanced itself from the comments saying Mr Carson was expressing a personal opinion and not that of the party.