Mr O'Brien polled 54 fewer votes than the Tory candidate
Former Labour health minister Mike O'Brien has lost Warwickshire North to the Conservatives by 54 votes.
Tory candidate Dan Byles polled 18,993 votes compared to Mr O'Brien's 18,939 votes. The pair were so closely matched that a recount was ordered.
Elsewhere the Conservatives' Marcus Jones won Nuneaton from Labour.
The Tories also gained Warwick and Leamington, and Jeremy Wright won the new constituency of Kenilworth and Southam, a notional Conservative hold.
There was a turnout of 81% in Kenilworth and Southam.
Labour's Bill Olner had defended Nuneaton since entering Parliament in 1992 but decided not to stand in 2010. Marcus Jones beat Labour's Jayne Innes by 2,069 votes.
In Warwick and Leamington, Conservative Chris White defeated Labour's James Plaskitt who had held the seat since 1997.
In Coventry North East, Labour Defence Secretary Bob Ainsworth held his seat with a large majority, despite losing 7.6% of his vote from the last general election.
Labour's Jim Cunningham held on to his Coventry South seat, as did Geoffrey Robinson in Coventry North West.
Conservative Mark Pawsey won in Rugby, a new seat, a notional gain from Labour.
The Conservatives held on to their seat in Stratford-upon-Avon. Nadhim Zahawi is the new MP after John Maples stood down.