The boards of Manchester United and Everton hae long been at loggerheads.
The strained relationship between the two clubs has seen Everton's attempts to sign Sergio Romero and Marcos Rojo from United hit a brick wall in the past 15 months, says the Daily Mail.
It is understood the animosity goes back to 2014, when United agreed to sell Tom Cleverley to Aston Villa for £7.5million.
Everton tried to hijack the deal while Cleverley was en route to his medical, but by the time their £5.5m bid was rejected by United it was too late for his transfer to Villa to go through.
Cleverley moved to Villa Park on loan instead, and joined Everton a year later on a free transfer.
The Glazer family are said to have held a grudge against the Toffees ever since, and that played a part in the collapse of negotiations over Romero and Rojo.