United have a broad agreement in place to sign the Netherlands international, who Erik ten Hag has made his top summer transfer target.
But Barcelona have maintained they do not wish to sell De Jong with club president Joan Laporta claiming they have ‘turned down offers’ for him.
A £63m fee, with a further potential £8.47m in add-ons, has been agreed with United and Barcelona have reportedly informed De Jong they need to sell him in order to alleviate some of the financial pressure on the club.
However, the situation is further complicated by the fact the midfielder is owed €17m in deferred payments and Barcelona boss Xavi has told De Jong he can stay if he is prepared to lower his current salary.
Speaking about the De Jong transfer saga, United legend and pundit Neville said the 25-year-old should consider taking legal action against Barcelona and has called for FIFPRO – the international players’ union – to intervene.
‘De Jong should consider legal action [versus] Barcelona and all players should be behind him!’ Neville posted on Twitter on Monday.
‘A club spending fortunes on new players whilst not paying the ones they have under contract their full money is immoral and a breach.
‘@FIFPRO should be all over bullying like this and stop it.’
Meanwhile, Harry Maguire has snubbed a potential move to Barcelona during United’s negotiations for De Jong, according to reports.
Reports last month claimed that Barcelona asked United if Maguire could be included as part of the deal that would enable De Jong to move to Old Trafford.
United have already secured deals for Christian Eriksen, Tyrell Malacia and Lisandro Martinez as they look to improve on last season’s sixth-place Premier League finish.
Their season gets underway on August 7 when they host Brighton at Old Trafford.
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