Vaughan Gething has dodged fresh questions over his acceptance of £200,000 in controversial donations to his recent Welsh Labour leadership campaign.
The First Minister, who is facing a no-confidence vote in the Senedd over the row, refused to answer queries from a BBC reporter at a Welsh language festival.
Mr Gething has faced weeks of scrutiny over the six-figure sum donated to his campaign from a man convicted of environmental crimes.
He took the money from the Dauson Environmental Group, which is owned by millionaire businessman David Neal, as he campaigned to replace Mark Drakeford as Welsh Labour leader.
The BBC has now reported that Resources Management Limited, another of Mr Neal's firms, was subject to a criminal investigation by Natural Resources Wales at the time Mr Gething accepted the cash.
Footage of a BBC reporter approaching Vaughan Gething at Urdd Eisteddfod in Maldwyn, Powys, on Friday showed the Welsh First Minister refusing to answer questions
Mr Gething last week teamed up with Labour leader Sir Keir Starmer on the general election campaign trail
Footage of a BBC reporter approaching Mr Gething at Urdd Eisteddfod in Maldwyn, Powys, on Friday showed the First Minister refusing to answer questions.
Mr Gething said: 'I've answered lots of questions about donations and I'm here at the Urdd to meet businesses here, and I've got lots of people to see and I'll be more than happy to answer more questions in the Senedd no doubt.'
The BBC reported that Mr Gething later told them today: 'Why on earth would I have known about an investigation at that time?
'I've complied with all the rules throughout the process and the BBC have said today there's no evidence at all that I have broken any rules in the contest.'
Asked when he first knew about the criminal investigation, Mr Gething said he 'found out when it was reported'.
Resources Management Limited said it would 'continue to fully cooperate with any pending investigations by Natural Resources Wales'.
Mr Gething last week teamed up with Labour leader Sir Keir Starmer on the general election campaign trail.
Andrew RT Davies, leader of the Welsh Conservatives, said: 'Vaughan Gething's donations just don't pass the smell test.
'So desperate was he to be First Minister, he accepted this dirty money despite the misery these firms have caused.
'And so desperate is Keir Starmer to be prime minister, he is prepared to stand with Vaughan Gething on this issue.
'It's time to restore integrity to the office of First Minister.'
Mr Gething, who has been the Welsh Labour leader since March, faces a no-confidence vote in the Senedd on Wednesday after being beset by scandal.
As well as the donations row, the First Minister has faced allegations he may have deleted messages that could be of interest to the Covid Inquiry.
The Welsh Government today said the timing of the no-confidence vote would force Mr Gething to miss the national D-Day commemoration in Portsmouth.
All opposition Senedd members - including Plaid Cymru and the Welsh Liberal Democrats leader Jane Dodds - are expected to support the Conservative motion.
Labour holds 30 of the 60 seats in the Senedd, so for the vote of no confidence to succeed at least one Labour MS would need either to vote in favour of the motion or abstain.
Plaid Cymru leader Rhun ap Iorwerth told Sky News' Sunday Morning with Trevor Phillips programme that his party would support the no-confidence motion.
Mr ap Iorwerth said: 'We have no confidence in the First Minister. More importantly than that, the Welsh public don't have confidence in him.
'But it's Labour who will decide – Labour members of the Senedd in that vote of no confidence, but crucially also Keir Starmer, who has shown through his parachuting of candidates last minute to Wales that he very much wants to act as the puppet master within all of the Labour Party.'