The leader of the UKIP and Independent Group at Norfolk County Council has resigned.
Toby Coke, who has led the 12-strong group at County Hall since his election in May 2013, informed his party colleagues of his decision by email today.
It is understood that Mr Coke will sit on the council as an unaligned independent until the elections in May and does not intend to stand again.
In his email, Mr Coke said his decision was 'following unresolvable issues', but it is not yet clear what that refers to.
Mr Coke, who represents Gayton and Nar Valley, has been contacted for comment.
Denis Crawford, who represents Thetford East, is the group's deputy leader and is expected to step up to lead the group.
Mr Coke was a member of UKIP's national executive committee. He runs his family's estate at Weasenham, which includes the outdoor recreation centre ExTREEme Adventure.
Last year, there was a call from within Mr Coke's own party for him to resign after he suggested UKIP should consider not standing against Conservative Brexiteers in the next general election.Glenn Tingle, UKIP's parliamentary candidate for Norwich North in 2009. 2010 and 2015, responded angrily to that suggestion.
Mr Coke's resignation comes just a day after Paul Nuttall, the party's leader at a national level spoke in Great Yarmouth.
Mr Coke had played a key role in the formation of the rainbow alliance at Norfolk County Council after the elections of 2013. The Conservatives took back control last year.
His decision comes six weeks before all 84 seats on Norfolk County Council are up for election.
The political makeup of the Conservative-controlled council following Mr Coke's resignation from UKIP is: 42 Conservative, 14 Labour, 11 UKIP and Independent, 10 Liberal Democrat, three Green, three non-aligned, and one vacancy.
George Nobbs, leader of the Labour group at County Hall, said: 'I always found, despite our obvious political differences between our parties, I always found Toby to be a man of great integrity who, when he gave his word, always kept it.
'It was due to his leadership we were able to form the rainbow alliance for three years for the good of Norfolk.
'He is a considerable political figure in East Anglian politics and beyond.'
Jonathon Childs, UKIP councillor for East Flegg, said: 'It's rather shocking that Toby has stood down, he has achieved great things for the UKIP group at County Hall,
'Norfolk really does owe him a great debt. He worked tirelessly to halt the incinerator at King's Lynn, he made huge inroads in addressing the democratic deficit by replacing the cabinet system with a much fairer committee system of governance.
'The UKIP group worked with the rainbow alliance to achieve these two hugely important things for Norfolk.'
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