Health minister Melanie Johnson has lost her seat in Welwyn Hatfield in Hertfordshire to the Conservatives.
Health minister Melanie Johnson lost her seat in Welwyn Hatfield
Grant Shapps, 36, chairman of the design, print and web firm PrintHouse Corporation, won the seat with 22,172 votes - a majority of 5,946.
Ms Johnson, 50, won Welwyn Hatfield in 1997 and again in 2001.
In response to the defeat the former schools inspector said: "I'm disappointed but, to be honest, I didn't expect to win."
She was made minister for public health in the June 2003 reshuffle.
"It was one of the most marginal seats in the country and you can only buck the trend so far," she said.
"I am very, very proud of the things we have done nationally... we need to do more to get that message across," she added.
Mr Shapps, who was defeated by Ms Johnson in 2001, said: "I've been working hard on this for six years. You can say I'm pleased."
Two other major seat changes took place in Bedfordshire and Buckinghamshire.
In Mid Bedfordshire the Conservative Nadine Dorries gained from the Independent Conservatives.
In Milton Keynes the Conservative Mark Lancaster gained from Labour's Brian White with a majority of 1,665.
In Bedfordshire the Conservative candidate Andrew Selous has held on to Beds South West with an increased majority.
The director of the Conservative Christian Fellowship retained the seat with 22,114 votes, a majority of 8,277 (6.14%) over Labour's Joyce Still.
Mr Selous - a former Territorial Army officer - was first elected to the House of Commons in 2001 with a majority of 1.8%.
In Luton Labour held on to both seats but with reduced majorities.
Labour's Kelvin Hopkins held on to Luton North with 19,062 votes, but with its majority reduced by 7.98%.
The Conservatives Hannah Hall came second with 12,575 votes.
Labour's Margaret Moran held on to Luton South with 16, 610 votes, but with a majority reduced by 12.51%.
The Liberal Democrat's Qurban Hussain had a gain of 11.65%.