Key UK by-elections in Scotland
A Westminster by-election is being held in the seat of Inverclyde, following the death of sitting Labour MP David Cairns.
Here is a look back at recent key UK by-elections in Scotland.
Friday 13 November, 2009 - Glasgow North East
Result: Labour win Majority: 8,111.
This high-profile by-election was held in the wake of Michael Martin's resignation from parliament and as Commons speaker.
Mr Martin, originally elected as a Labour MP went in the wake of the MP expenses scandal.
In the end, Labour saw off an SNP challenge to comfortably win a by-election which saw a record low turnout and the BNP coming in fourth place, with the Liberal Democrats in sixth.
By-election breakdown: Willie Bain (Labour) 12,231; David Kerr (SNP) 4,120; Ruth Davidson (Tory); 1,075 votes; Eileen Baxendale (Lib Dem) 474.
FRIDAY 7 NOVEMBER, 2008 - Glenrothes
Result: Labour hold Majority: 6,737 Swing: 4.9% from Labour to SNP.
This by-election, in the seat neighbouring Gordon Brown's constituency, was held after the death of sitting MP John MacDougall.
Labour held the seat with a comfortable majority in the face of a strong SNP challenge - the Tories and Lib Dems came some way behind and both candidates lost their deposits.
By-election breakdown: Lindsay Roy (Labour) 19,946; Peter Grant (SNP) 13,209; Maurice Golden (Con) 1,381; Harry Wills (Lib Dem) 947.
Friday 25 July, 2008 - Glasgow East
Result: SNP gain Majority: 365 Swing: 22.5% from Labour to SNP.
Labour lost one of its safest Scottish seats when the SNP overturned a majority of 13,507 to win by just a few hundred votes.
The Tories came third in the contest, sparked by the resignation of sitting MP David Marshall on health grounds, while the the Lib Dems took fourth position.
Labour re-claimed the seat at the 2010 UK election.
By-election breakdown: John Mason (SNP) 11,277; Margaret Curran (Lab) 10,912; Davena Rankin (Con) 1,639; Ian Robertson (Lib Dem) 915.
Friday 10 February, 2006 - Dunfermline and West Fife
Result: Liberal Democrat gain Majority: 1,800 Swing: 16.24% from Labour to Lib Dems.
The Liberal Democrats overturned Labour's majority of more than 11,500 in the constituency, which neighbours Gordon Brown's Kirkcaldy and Cowdenbeath seat.
Willie Rennie was declared the victor with 12,391 votes in the by-election, which was called after the death of sitting MP Rachel Squire. Labour came second.
Labour won the seat back in the 2010 General Election, while Mr Rennie went on to become an MSP and Scottish Lib Dem leader.
By-election breakdown: Willie Rennie (Lib Dem) 12,391; Catherine Stihler (Lab) 10,591; Douglas Chapman (SNP) 7,261; Carrie Ruxton (Cons) 2,702.
Thursday 29 September, 2005 - Livingston
Result: Labour hold Majority: 2,680 Swing: 10.22% from Labour to SNP.
The Livingston by-election was called following the sudden death during a hill walking trip of the sitting MP and former cabinet minister Robin Cook.
His former election agent and trade unionist Jim Devine held the seat for Labour, but its majority fell from 13,000 at the General Election earlier that year to 2,680.
Devine went on to be jailed for 16 months for fraudulently claiming £8,385 in expenses.
At the time of the Livingston by-election, Labour also held the Holyrood seat of Glasgow Cathcart, made vacant following former MSP Lord Mike Watson's conviction for wilful fire-raising.
By-election breakdown: Jim Devine (Lab) 12,319; Angela Constance (SNP) 9,639; Charles Dundas (Lib Dem) 4,362; Gordon Lindhurst (Cons) 1,993.
Thursday 21 December, 2000 - Falkirk West
Result: Labour hold Majority: 705 Swing: 16.1% from Labour to SNP.
This by-election was triggered by the resignation of Dennis Canavan, who won the seat for the party, but later took the constituency at Holyrood as an independent, after being excluded from Labour's candidate list.
The Labour Party fought the contest on the premise that voters should still elect a Labour successor and narrowly hung onto the seat.
By-election breakdown: Eric Joyce (Lab) 8,492; David Kerr (SNP) 7,787; Craig Stevenson (Con) 1,621; Hugh O'Donnell (Lib Dem) 615.
Thursday 23 November, 2000 - Glasgow Anniesland
Result: Labour hold Majority: 6,157 Swing: 6.5% from Labour to SNP.
Labour easily held onto the seat, which became vacant following the death of Scotland's first first minister, Donald Dewar.
The night was a double by-election victory for Labour - Mr Dewar also held the seat at the Scottish Parliament, which went to left-winger Bill Butler with a majority of more than 6,000.
By-election breakdown: John Robertson (Lab) 10,359; Grant Thoms (SNP) 4,202; Dorothy Luckhurst (Con) 2,188; Chris McGinty (Lib Dem) 1,630.
Friday 24 September, 1999 - Hamilton South
Result: Labour hold Majority: 556 Swing: 22.56% from Labour to SNP.
Labour only just hung onto the seat after the sitting MP and then defence secretary, George Robertson, quit parliament to become Nato secretary general.
The 15,878 majority Mr Robertson achieved at the 1997 General Election was partly eroded by the SNP vote and the Scottish Socialist Party, which came third, ahead of the Conservatives and Liberal Democrats.
By-election breakdown: Bill Tynan (Lab) 7,172; Annabelle Ewing (SNP) 6,616; Shareen Blackhall (SSP) 1,847; Charles Ferguson (Con) 1,406; Marilyne MacLaren (Lib Dem) 634.