Labour Assembly Member Alun Davies has called for an urgent inquiry by the Labour party into their candidate in Carmarthen East and Dinefwr.
Maria Carroll, who is challenging Plaid Cymru MP Jonathan Edwards in the seat, was alleged in the Daily Mail to have run a secret Facebook group which advises members how to avoid expulsion from the party.
According to the paper, some of those who joined the group had posted content denying the holocaust elsewhere on the site.
The paper alleges that the group Labour Party Compliance: Suspensions, Expulsions, Rejections Co-Op advised more than one Labour Party member who had posted such content.
Maria Carroll told the Daily Mail that she had not seen the posts referred to, which were not posted in the Facebook group that she ran.
Alun Davies, who represents Blaenau Gwent in the Senedd, called for an inquiry into the matter.
“I trust that Welsh Labour will lead an urgent inquiry into this,” he said. “And report before polling day.”
Positif Politics director Daran Hill said that it was the first time that serious accusations of antisemitism had been made within Welsh Labour.
“Until now Welsh Labour has remained pretty untouched by charges of antisemitic behaviour,” he said.
“A key issue now is to what extent was Welsh Labour involved in the actual candidate selection and, most particularly, what vetting was undertaken by Welsh General Secretary Louise Magee.
“This can’t just be painted as an English problem any more.”
Jonathan Edwards called on Labour to withdraw their support for Maria Carroll pending the result of an investigation.
“Antisemitism is racism pure and simple,” he said.
“The Labour party should remove official support for their candidate in Carmarthen East and Dinefwr pending an investigation into these very serious allegations.”