Labour candidate Andy Sawford has won the seat in the Corby and East Northamptonshire by-election.
Andy Sawford won by 7,791 votes, with Conservative candidate Christine Emmett in second. The UK Independence Party came third and the Liberal Democrats fourth.
The seat, which covers Oundle and several villages in the Mercury area including Collyweston, King’s Cliffe, Easton-on-the-Hill and Gretton, was vacated by Tory MP Louise Mensch.
There are 14 candidates fighting for the seat.
If Labour wins, it will be the party’s first gain from the Conservatives at a by-election since 1997.
The turnout figure has been confirmed at 44.8 per cent, with the result expected to be announced soon.
Ahead of the election, Mrs Mensch said on Twitter that she took responsibility if Conservative candidate Christine Emmett, a Rutland county councillor, failed to retain the parliamentary seat.
She Tweeted: “Election result will not be a verdict on either Christine, or the Conservatives, but only on the decision I took to step down mid-term.
“Though I had to resign to unite our family, there was large and entirely local anger. I wish I had been able to see out my term.
“Christine and her team did an incredible job in the most difficult possible circumstances. I know she will one day make a wonderful MP.”
Results in full
BISHOP, David Laurence (Elvis Loves Pets Party) 99
EMMETT, Christine (The Conservative Party Candidate) 9,476
GILLMAN, Ian Francis (Independent) 212
HOPE, Jill Susan (Liberal Democrat) 1,770
HORNETT, Jonathan Terence (The Green Party) 378
KAPUR, Rohen (Young People`s Party UK) 39
LOTUN, Adam Ismael (Democracy 2015) 35
MOZZARELLA, Mr (Independent) 73
PARKER, Margaret Lucille Jeanne (UK Independence Party) 5,108
REYNOLDS, Peter John (Cannabis Law Reform) 137
RIDDELL, Gordon (British National Party) 614
SAWFORD, Andrew (Labour Party Candidate) 17,267 Elected
SCOTTON, Christopher Craig (United People`s Party) 25
WICKHAM, David (The English Democrats - “Putting England First!”) 432