The 66-year-old was expelled from Labour in 2003 and he has been a thorn in the party’s side ever since, beating their candidates to claim shock victories on two occasions.
Who is George Galloway?
Mr Galloway was born in Dundee in 1954 and educated at the city's Harris Academy before he began working at a Michelin tyre plant.
He joined the Dundee Labour Party at 13 and held several positions before becoming the youngest ever chairman of the Scottish Labour Party in March 1981, at the age of 26.
Quickly establishing himself as a vocal activist, he ran a number of controversial campaigns, including one which called for Dundee to be twinned with the Palestinian West Bank town of Nablus.
In June 1987, he joined the House of Commons for the first time, when he ousted the Social Democrat Party's Roy Jenkins to become MP for Glasgow Hillhead.
His career in the Commons began with controversy, as he made comments about having “sexual intercourse” when he visited Mykonos in Greece shortly after he was elected and the following year the executive committee of his constituency Labour Party passed a vote of no confidence, although he narrowly survived to win reselection the following year.
He also faced questions over his role as general secretary of the charity War on Want and allegations that funds had been misused. He was cleared following an independent investigation and an audit, but agreed to pay contested expenses.
In 1997, he became MP for Glasgow Kelvin, after his old constituency was abolished, and then won re-election in 2001.
While taking a close interest in the Middle East and repeatedly criticising Israel, he also rebelled against the party whip on dozens of occasions before he was expelled in 2003.
He was found guilty of bringing the party into disrepute after he made several divisive comments about the Iraq war and publicly accused Tony Blair and President George Bush of acting "like wolves", but he claimed to have been the victim of “a politically-motivated kangaroo court”.
What did he do after leaving Labour?
In 2005, Mr Galloway caused a massive upset when he overturned a Labour majority in London’s Bethnal Green and Bow to become the Respect Party's first MP.
After switching to the London constituency of Poplar and Limehouse, he lost to Labour’s Jim Fitzpatrick in 2010, but two years later, he claimed another surprising election victory when he beat Labour once again to become the MP for Bradford West.
He has not returned to the Commons since he was defeated in 2015, but continued to make headlines.
He campaigned for Brexit and against Scottish independence, attempted to unseat former Labour deputy leader Tom Watson at the 2019 General Election, and founded the All for Unity party.
Until 2019, he also worked as a broadcaster but was sacked by talkRADIO after sending an allegedly anti-Semitic tweet.
He celebrated the defeat of Tottenham to Liverpool in the Champions League final saying it meant there would be “No #Israel flags on the Cup”.
Why is he standing in Batley?
In May, Mr Galloway announced he is running in the forthcoming Batley and Spen by-election in a bid to oust Sir Keir Starmer as leader of the Labour Party.
When he revealed he was standing as a candidate for his Workers Party of Britain in the poll on July 1, he said: “If Keir Starmer loses this by-election, it’s curtains for Keir Starmer.”