Len McCluskey has been re-elected as Unite’s general secretary following a bitter leadership battle.
The result will be seen as a boost for Labour leader Jeremy Corbyn.
Mr McCluskey’s chief rival Gerard Coyne was seen as the anti-Corbyn candidate and Unite is the party’s biggest donor.
Mr Coyne was suspended from his job as a Unite official on Thursday pending an investigation but he remains a member of the union.
He faces accusations of bringing the union into disrepute over claims made during the contest, which saw barbs flying from both sides.