United have made a flying start to the season, scoring 12 goals to collect 10 points from their opening four league games.

Mourinho, whose team host Everton on Sunday, led Chelsea to three Premier League titles, but the Portuguese tactician feels it has never been tougher in England.

“I think it is more difficult now,” he said. “The economic power belongs to everyone.

“When you speak about economic power, it is not just to buy but to keep players and say, ‘No, we don’t sell’. That power belongs to every club in the Premier League, so the teams are potentially strong.

“But it was always difficult for different reasons. It is difficult because this is the country with more teams that fight for the title.

“And with more teams outside that group of six or seven who have conditions to give you hard matches and to take points off you.

“It is difficult because it is competitive. It is the most difficult country in which to win the title.”

United showcased some of their economic power in the off-season, including buying Romelu Lukaku for a reported £75million from Everton.

Mourinho played down his impact in landing the Belgium international, who has already netted six goals this season, amid apparent interest from Chelsea.

“I don’t think it was my influence, no,” he said.

“I think that we paid the money that Everton asked for and we paid the player the wages that his agent asked for and we paid the agents the commission that they asked for.

“I don’t see another reason.”