Manchester City have been threatened by Manchester United's new investor Jim Ratcliffe over being pushed off their perch at the top of English football.

Sir Jim Ratcliffe and INEOS completed their purchase of a minority stake in Manchester United on Tuesday evening.

Joel Glazer, executive co-chairman, said in reaction to the news, "I would like to welcome Sir Jim as co-owner and look forward to working closely with him and INEOS Sport to deliver a bright future for Manchester United."

Now, speaking during his first public interview since his 27.7 per cent stake in Manchester United was confirmed this week, Jim Ratcliffe said that while the Old Trafford club have a lot to learn from rivals Manchester City and Liverpool, they are the "enemy".

"We have a lot to learn from our noisy neighbour (Manchester City) and the other neighbour (Liverpool)," the 71-year-old told the media this week.

"They are the enemy at the end of the day. There is nothing I would like better than to knock both of them from their perch."

Despite the brief threat to the future of the Etihad and Anfield clubs, Ratcliffe went on to stress his respect for the organisations at both teams, with previous reports pointing towards his close working relationship with City chairman Khaldoon Al Mubarak.

"Equally we are the three great northern clubs who are very close to one another," Ratcliffe continued. "They have been in a good place for a while and there are things we can learn from both of them.

"They have sensible organisations, great people within the organisations, a good, driven and elite environment that they work in. I am very respectful of them but they are still the enemy."

Manchester United have already began work on reshaping their football-focussed hierarchy, snatching Manchester City chief Omar Berrada from the Etihad Stadium, and moving the experienced professional into their role of CEO at Old Trafford.

United are also keeping an eye on former Manchester City academy director Jason Wilcox for a senior role within their operation, just one year after Wilcox left the Etihad Stadium to take up the role of recruitment head at Southampton.