Firebrand politician George Galloway, running for his Respect Party, won a sensational return to parliament on Friday in the Bradford West by-election, dealing a heavy blow to his former party, Labour, which had held the seat for decades.

Galloway claimed 18,341 votes, over 10,000 more than Labour candidate Imran Hussain, confounding pre-poll expectations.

"This is the most sensational victory in British by-election history," the renegade MP claimed in his victory speech.

The winning candidate called the result an "uprising", which will spark a "Bradford Spring".

He also wished "political perdition" on the Conservative/Liberal Democrat coalition, and urged Labour to leave the "path of treason set for them by Tony Blair."

Galloway served as an MP from 1987 to 2010, but was expelled from the Labour Party in 2003 after publicly denouncing Britain's involvement in the Iraq invasion.

The 57-year-old, who was once a contestant on reality television show Celebrity Big Brother, attempted to overturn economic sanctions against Iraq in the 1990s and 2000s and also met former dictator Saddam Hussein during one visit.

The Scottish firebrand gained international notoriety in 2005 when he defended himself in the US Senate over claims he received illicit payments from the United Nations' Oil for Food Programme.

Galloway used the platform to turn the tables on his accusers, launching a scathing attack on US policy in Iraq.

Labour candidate Hussain was overwhelming favourite to claim the parliamentary seat ahead of Thursday's vote, which was called after incumbent Marsha Singh resigned due to ill health.