De Jong has been on United’s radar since the start of the summer with La Blaugrana aiming for a potential deal in the region of €85m.
Despite Barcelona being open to a possible exit, de Jong has maintained his stance of wanting to stay in Catalonia next season.
United are still monitoring the situation but the Dutch international is locked in talks to continue his contract at the Camp Nou.
Club president Joan Laporta has previously stated the need for de Jong to take a pay cut to remain as part of a financial balancing act at the club.
The former Ajax playmaker is also chasing owed wages, deferred from during the 2019/20 season, alongside an automatic contract renewal this summer.
Neville slammed Barcelona for misleading de Jong over their monetary position as he edges away from joining United in the coming months.
“De Jong should consider taking legal action against Barcelona and all players should stand behind him!” the former England international posted on Twitter.
De Jong should consider legal action v Barcelona and all players should be behind him!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.
— Gary Neville (@GNev2) July 25, 2022
“A club that spends fortunes on new players without paying those under contract their full money is immoral and in breach of contract.
“FIFPRO should end with the harassment of this type and stop it.”