According to the Manchester Evening News, the Portuguese has again sought assurances United would be prepared to back him in the transfer market, either in January or next summer. It is understood the 54-year-old feels he deserves the club's full support in the transfer window, after delivering two trophies in his first season at Old Trafford.
United splashed £140.9m in the transfer window last summer as they signed Romelu Lukaku, Nemanja Matic and Victor Lindelof but Mourinho did not hide his frustration as the club failed to secure the fourth signing he craved.
Inter Milan winger Ivan Perisic and Real Madrid forward Gareth Bale were both closely monitored by United, but the former remained in Italy after United refused to meet Inter's valuation, while the Welshman never seemed particularly eager to swap the Spanish capital for Manchester.
City, meanwhile, outspent United by over £70m, as Pep Guardiola moved to address the issues that had derailed his side during his first campaign in the Premier League and is now reaping the benefits of his summer business.
The latest rumours of discontent come as Mourinho's agent, Jorge Mendes, has reportedly made contact with PSG, after his client spoke of his admiration for the French giants last month.
During an interview with French TV station TF1 the day after United drew 0-0 at Anfield, the Portuguese admitted he would not end his career at Old Trafford, despite previously claiming he could stay at his current club for 15 years.
"The other day my son who lives in London went to Paris and not to Manchester to watch the match," Mourinho, whose contract expires in 2019, said. "At the moment in Paris there is something special. Magic, quality, youth, it's fantastic."
Mourinho then repeated the claims in his press conference ahead of United's Champions League tie away at Benfica, but pointed out it was because he believed it is now "impossible" to remain at a club for as long as the likes of Sir Alex Ferguson and Arsene Wenger.
PSG's financial clout is arguably even bigger than City's, as demonstrated by a summer during which they smashed the world's transfer record by paying £198m for Neymar and committed to buy Kylian Mbappe for £166m from Monaco next summer, after signing him on a season-long loan.
The coming summer promises to be a very important one for United, who have a number of players either out contract or entering their last 12 months of their deal. Zlatan Ibrahimovic, Michael Carrick and Marouane Fellaini fall in the former category, while Juan Mata, Ander Herrera, Luke Shaw, Daley Blind, Ashley Young and Sam Johnstone are in the latter.
United could retain the six by triggering a one-year extension on their deals, but the club are yet to indicate they are willing to do so.