Mark Reckless of UKIP has lost his seat in Rochester and Strood to the Conservatives and party leader, Nigel Farage, has failed to be elected in South Thanet.
Rochester and Strood was won by Conservative candidate Kelly Tolhurst with a majority of more than 7,000.
In November, Mr Reckless fought a by-election in the constituency, beating Ms Tolhurst.
Mr Farage has resigned as party leader following his defeat in South Thanet.
The Conservative candidate Craig Mackinlay took the South Thanet seat with a majority of 2,812.
He said: "I'm delighted. I've given promises on Manston Airport and we're working, leaving no stone unturned, to make sure it opens.
"I've got a fairly unique plan for the regeneration of Ramsgate."
Mr Mackinlay, a former UKIP leader and Medway councillor, takes over the seat from Laura Sandys, who stood down as Conservative MP at the election.
Mr Reckless, who held the seat at a by-election after defecting from the Conservatives to UKIP, said: "I always knew what I was doing was a risk but nobody should underestimate UKIP's achievement.
"I am proud to have been a part of that and to have represented the people of Rochester and Strood for the past five years."
The BBC's political correspondent, Ellie Price tweeted; "Mark Reckless tells new Rochester & Strood MP Kelly Tolhurst: 'Never ever forget who your bosses are.'"
Labour came third with just over 10,000 votes, while the Lib Dems came fifth to the Green Party with 1,251 votes.
Tories retain seats
The Conservatives have held Chatham and Aylesford, with Tracey Crouch retaining her seat, with a share of just over 50% of the votes.
Conservative Roger Gale has kept his Thanet North seat with a majority of almost 11,000 over the UKIP candidate Piers Wauchope.
Rehman Chishti has retained his seat in Gillingham and Rainham for the Conservatives, with a majority of more than 10,000 votes.