Controversial moves to scrap the Mid-Derbyshire Parliamentary Constituency have effectively been mothballed.
Under plans backed by the Tories the seat, held by Pauline Latham MP, would have become part of a new Amber Valley constituency.
Duffield would have been absorbed into the Derbyshire Dales constituency.
Meanwhile, West Hallam, Dale Abbey, Ockbrook, Borrowash and Breadsall would have been returned to the Erewash constituency.
However, MPs have now voted by 334 to 292 to postpone the shake-up until 2018 at the earliest.
It was the first time the Lib Dems had voted against their Conservative coalition colleagues in the House of Commons.
The changes would have meant the end of Mrs Latham’s career.
However, she said she would have given the proposals her backing for the greater good of the UK.
Mrs Latham said: “Although the boundary review proposed abolishing my constituency and hence ending my Parliamentary career.
“I supported and voted for the Boundary changes as they were in the best interests of the country and British democracy.”
Officers from the Boundary Commission for England suggested the changes along geographical, non-political lines.
Parliament agreed in principle in 2011 to reduce the number of MPs and to redraw the electoral map to make all constituencies roughly the same size in terms of number of voters.
Some believe the proposals, which were backed at the time by both coalition parties, would help the Conservatives win up to 20 extra seats at a future election.
A number of Conservative MPs attacked their coalition partners for changing their position on the boundary review.
The issue of boundary changes has been one of the biggest flashpoints between Prime Minister David Cameron and his deputy Nick Clegg since the two entered government together.