Report from ITV Wales Political Editor Adrian Masters
The prime minister has been urged to "take robust action" to investigate the Senedd members who are alleged to have breached coronavirus rules in the Welsh Parliament.
Plaid Cymru MP Liz Saville Roberts has written to Boris Johnson following reports a group of politicians, including three Conservative MSs, took part in a social gathering on the Senedd estate.
The incident happened on December 8, four days after a ban on the sale, supply and consumption of alcohol on licensed premises came into force, although off-licences were allowed to sell alcohol until 10pm.
Former Welsh Government minister Alun Davies allegedly consumed alcohol with Welsh Conservatives leader Paul Davies, chief whip Darren Millar and the party's chief of staff Paul Smith in a Senedd tea room.
All four men deny breaking Covid-19 rules and say they observed social distancing while meeting to discuss working together on a proposed bill, and consumed alcohol not bought from parliament premises.
Mr Davies was suspended from the party's group following the allegations.
Ms Saville Roberts wrote to Mr Johnson on Wednesday and said because the leader of the Conservative group and Chief Whip in the Senedd are "implicated", "it falls on you as leader of the Conservative party to take robust action pending a thorough investigation."
The letter continued, "It is vital that public confidence is not undermined due to this episode. Withdrawing the party whip as a first step would at least provide some reassurance that the Conservative party is taking the matter seriously".
Paul Davies has previously said that Covid rules "shouldn't be broken".
In an interview with ITV Wales national correspondent Rob Osborne on Sharp End, Mr Davies said, "I don't think anybody should break the rules - the rules are there whether you're travelling to Barnard Castle or you were travelling to buy some chips - no one should be breaking the rules.
The Prime Minister's Press Secretary Allegra Stratton said Boris Johnson is yet to speak to Paul Davies.
She added, "As we've said many times before, the Prime Minister expects everybody, no matter their standing, no matter their status, to be sticking to the rules as well as they are able. The Prime Minister needs everybody, no matter their status or position in life to be going above and beyond in following the rules on Covid."
It comes as the health minister was quizzed on the matter during the coronavirus press conference. He said, "I don't think I should then lay in on an issue like this where I'm simply not aware of all the facts. The Senedd authorities are conducting their own investigation and I'm sure there will be interest in that," he said.
Mr Gething told a press conference in Cardiff that he was not aware of "all the facts" of the matter, which took place in early December, with an investigation by the Senedd Commission due to establish what happened.