The boss of the Unite union, Len McCluskey, has denied allegations the union planned to join with and fund Momentum - a key group which supports Jeremy Corbyn - in order to take over the Labour Party.
The row erupted on Monday after recordings of Momentum head Jon Lansman were leaked to the media, revealing a supposed plan to formally join forces with Unite if McCluskey - who is running to maintain his leadership of the union - is re-elected.
This would reportedly create a power base to ensure the two groups maintain control of Labour when Mr Corbyn steps down.
The recordings prompted a furious reaction from deputy leader Tom Watson, who argued with Lansman publicly on Twitter.
Now, McCluskey has stepped in, saying the claims of a takeover were a "complete fabrication" and insisting there had been no "secret meetings" or any plans to provide funding to anyone.
He fired back at Watson, saying he and "other right-wing Labour MPs would be best keeping their noses" out of Unite business as Unite members would reject any attempts for other people to take over the union.