A Labour general election candidate has been referred for an internal party investigation over anti-Semitism allegations.
Maria Carroll is accused of previously running a Facebook group that included people alleged to have made anti-Semitic comments.
First Minister Mark Drakeford said he was “concerned” about reports in the Mail on Sunday regarding Ms Carroll.
She said she had not seen the relevant social media posts.
Ms Caroll, the Welsh Labour candidate for Carmarthen East and Dinefwr, added that she would have “immediately condemned them” had she seen the comments.
The Facebook group, whose contents are only available to group members, was reportedly set-up in order to advise Labour members subject to internal party disciplinary investigation on how to defend themselves.
Ms Carroll said: “I joined that group when left wing members were being suspended from the Labour Party en masse to prevent them from voting in the 2016 Labour leadership election, for incidents as small as retweeting [former Green Party leader] Caroline Lucas.
“When the group took an anti-Semitic conspiratorial direction I left it.”
Labour’s former Peterborough Council candidate, Alan Bull, was reportedly a member of the closed Facebook group.
He withdrew as a candidate after acknowledging it was a “bad mistake” to share an article on Facebook in 2015 which suggested the Holocaust was a hoax.
Ms Carroll said she did not see the “horrific social media posts” by Alan Bull as “these posts were not made in the group” she was in.
She added: “I’ve been an outspoken critic of anti-Semitism in our party, including calling out anti-Semitic abuse towards [former Labour MP] Luciana Berger and anti-Semitism denialism within our party.
“I’ve been blocked by anti-Semitic accounts as a result.”
Welsh Labour became aware of the accusations against Maria Carroll after being approached by the Mail on Sunday on Friday night.
In a statement on Sunday, Welsh Labour leader and first minister, Mark Drakeford said: “I am of course concerned of reports on the actions taken by Maria Carroll.
“Welsh Labour acted immediately and referred these matters to the Governance and Legal Unit of the UK Labour Party for investigation.
“I have consistently made it clear that anti-Semitism has no place in our party or in Wales,” he added.
Labour Assembly Member for Blaenau Gwent, Alun Davies, tweeted: “I trust that @WelshLabour will lead an urgent inquiry into this. And report before polling day [on 12 December].”
Owen Griffiths, who represents Labour on Vale of Glamorgan council, said on Twitter: “Support for this candidate should be pulled and she should be expelled from the party.”
Other candidates standing in Carmarthen East and Dinefwr include Plaid Cymru’s Jonathan Edwards, Havard Hughes for the Conservatives and the Brexit Party’s Peter Prosser.