The Conservatives' leader in the Welsh Assembly has quit the post after seven years following a spat over the future for jobs in Wales after Brexit.
Andrew RT Davies said in a statement that he had tendered his resignation "with deep regret" following a meeting of all Tory Assembly Members on Wednesday 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".
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, which he dismissed as "hyperbole".
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 and customs union.
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 the Welsh seat of 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."
Speaking after Wednesday's meeting, Mr Davies said: "It has been a huge privilege to serve in this position since 2011, after securing the mandate of the party in a ballot of the membership.
"It is my firm belief that any leader of the Assembly group should secure the same mandate in a full ballot of the grassroots, and I hope that my successor will emerge in that manner.
"I look forward to supporting whoever emerges from the contest to replace me, and I will continue to place all of my efforts into advancing the Welsh Conservative cause both here in Wales and Westminster."
Mrs May thanked Mr Davies for his service, adding: "Under Andrew's leadership, the Welsh Conservatives have provided a strong opposition to Labour in Cardiff Bay and a strong voice for the people of Wales, both at home and in Westminster.
"I know he will continue to be a passionate champion for the people of South Wales Central in the Assembly, as he has been for more than a decade - and will 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: "Despite our obvious political differences, I always found Andrew to be good company, and he never broke the confidences I shared with him as leader of the opposition.
"That is the sign of a decent and honest politician. Andrew has made his mark in Welsh politics, and his jovial and larger than life personality has always been a breath of fresh air during Assembly proceedings. I wish him well in the future."
Mr 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.