Voters are heading to the polls in the last few hours of English by-elections in Sedgefield and Ealing Southall.
Two contests are being held on the same day
A total of 23 candidates are standing in the two constituencies, previously both held by Labour.
The Sedgefield contest was triggered by the resignation of ex-PM Tony Blair and Ealing Southall by the death of Piara Khabra, the UK's oldest MP, at age 82.
Polls close at 2200 GMT with all the results expected to be by the early hours of Friday.
Sedgefield, in County Durham, was made vacant following the resignation of Mr Blair - on the same day he stepped down as prime minister - to become a Middle East peace envoy.
He had been MP for the seat - which he held with a majority of 18,449 at the last general election - since 1983.
Ealing Southall, in west London, had been represented by Mr Khabra since 1992. He had a majority of 11,440 at the last election.
The official list of candidates for Sedgefield is:
- Stephen Gash, English Democrats - "Putting England First"
- Paul Gittins, Independent
- Tim Grainger, Christian Party "Proclaiming Christ's Lordship"
- Chris Haine, Green Party
- Alan 'Howling Laud' Hope, The Official Monster Raving Loony Party
- Toby Horton, UK Independence Party
- Graham Robb, Conservative Party
- Norman Scarth, Anti-Crime Party
- Andrew Spence, British National Party
- Greg Stone, Liberal Democrat
- Phil Wilson, Labour Party
The list for Ealing Southall is:
- Nigel Bakhai, Liberal Democrats
- John Sydney Cartwright, The Official Monster Raving Loony Party
- Sati Chaggar, English Democrats - 'Putting England First!'
- Salvinder Singh Dhillon, Respect - Peace, Justice, Equality
- Sarah Janet Edwards, Green Party
- Kuldeep Singh Grewal, Independent
- Tony Lit, Conservative Party
- Yakub Masih, Christian Party 'Proclaiming Christ's Lordship'
- Jasdev Singh Rai, Independent
- KT Rajan, UK Independence Party
- Virendra Kumar Sharma, The Labour Party Candidate
- Gulbash Singh, Independent
The names of candidates and description of who they are standing for are as described on the returning officers' official lists.