The leader of the Conservative group in the Welsh Assembly, Andrew RT Davies, has quit the post after seven years.
Mr Davies sparked a row last week after accusing plane manufacturer Airbus of "hyperbole" over its warning it might have to switch production out of the UK as a result of Brexit.
In a statement this morning he says it is with 'deep regret' that he stands down from his post, following a meeting of all Tory Assembly Members this morning.
Prime Minister Theresa May sent her best wishes, saying she knew Mr Davies would "continue to speak up for the best interests of Wales as we leave the European Union and forge a new role for the whole United Kingdom on the world stage".
Labour's First Minister of Wales, Carwyn Jones, said Mr. Davies' "jovial and larger than life personality has always been a breath of fresh air during Assembly proceedings"
As one of Wales' most high profile 'Leave' campaigners, Andrew RT Davies was made famous by this Brexit speech as the Tory Party Conference in 2016.
Mr Davies was last week accused by a Government minister of making "inflammatory" comments about the warning of aircraft manufacturer Airbus that it could quit the UK over Brexit.
Airbus, which employs 6,400 people in Wales, has said it may have to reconsider the future of operations in the UK if Britain leaves the single market.
In response, Mr Davies said the company was "doing a disservice" to the workers which had made it successful, adding: "You'd think that Airbus was the first company to entertain slashing costs and by extension standards - and it doesn't usually end well.
"We are getting to the business end of the negotiations, and there is a lot of hyperbole flying around."
UK defence minister Guto Bebb, who represents Aberconwy, called on him to retract his "inflammatory" comments, saying: "Shooting the messenger is an unworthy position for a politician to take not least when that politician aspires to lead a government in Wales."
The announcement means the Welsh Conservatives will have leadership contests simultaneously with Welsh Labour and UKIP in Wales.
Andrew RT Davies was first elected to the Welsh Assembly as member for South Wales Central in 2007 and previously held shadow portfolios for transport and education.
ITV Wales' politics team has interviewed Mr Davies on numerous occasions. Including this interview after former UKIP AM Mark Reckless joined the Welsh Conservative Assembly group.
Mr. Davies said today that "politics is an unpredictable business", after Bishop Ryan Cleminson complained his meeting with the former leader was cancelled due to his resignation and he had travelled from Swansea to meet him .