One of the best-known figures in Britain's Labour Party for the last 20 years, Alastair Campbell, says he has been expelled for backing another party in last week's European Parliament election.

Campbell became a famous figure as the pugnacious spin doctor to then-Prime Minister Tony Blair between 1997 and 2003.

He remains a prominent commentator and has criticized the party's lurch to the left under current Labour leader Jeremy Corbyn and its failure to firmly back a new Brexit referendum.

Campbell tweeted Tuesday that "I am and always will be Labour" but that he had voted for the pro-EU Liberal Democrats in the European election "to try to persuade Labour to do right thing for country/party."

Labour said "support for another political party or candidate is incompatible with party membership."