The Tories have made gains in East Sussex, winning control of the county council, while maintaining their hold on West Sussex in local elections.
UKIP's support has collapsed, with its presence on both councils wiped out, mirroring the national trend.
Its group leader in East Sussex Philip Howson said: "People think Brexit is finished but it's not."
The Conservatives swept to victory, winning 11 new seats in the west of the county and eight more in the east.
For the past four years, no party had overall control of East Sussex.
The Conservatives now have 30 seats, up eight from 2013, while the Liberal Democrats gained two, bringing their total to 11.
UKIP lost all eight seats on the council. Labour is down three seats, to four.
UKIP's Mr Howson said he was "gutted" with the results.
He added: "Unfortunately, people are voting Labour and Conservative because they think Brexit is finished... but Brexit is nowhere near finished."
Liberal Democrat Philip Daniel narrowly took Ringmer. After the result, he urged local people to vote tactically at the general election on 8 June.
"If the Labour, Lib Dem and Green vote is split then Conservatives will win," he warned.
In West Sussex, the Tories held on, while the Liberal Democrats became the main opposition party.
The Conservatives now hold 56 seats, up 11, while the Liberal Democrats gained one, making their total nine.
Labour won five seats, down one; while UKIP lost all 10 of the seats it secured in 2013.
Analysis, by Peter Henley, political editor, BBC South
In West Sussex, the Conservatives won every one of the 10 seats held by UKIP. But defeated UKIP councillors somehow seemed not to mind.
They'd got what they wanted after all, and never really got into the mind-numbing business of council agendas and meetings and responsibility.
In a quiet way they were relieved, though pledging to be watchful that Theresa May didn't use a big majority to water Brexit down.
The more serious Conservative activists also urge caution. It's a long way to the 8 June.
As Conservatives know well, you can't rely on the voters to do everything you want.
Across England, Wales and Scotland, voters have had their say on a total of 4,851 council seats.
East Sussex County Council has seen a total of 50 councillors elected, while in West Sussex 70 members have been voted in.
Across England there are also eight mayoral elections, including elections in six new "combined local authorities".