Chelsea boss Jose Mourinho believes it will be "impossible" for clubs to compete with Manchester City if Financial Fair Play is not enforced.
City's vast spending in an era of Financial Fair Play has come in for repeated veiled criticism from Mourinho, who is keen to see how the economic regulations are explained and enforced by European football's governing body UEFA.
"If they (football's authorities) want to make it impossible (to compete with City), it's impossible," Mourinho said.
"(Chelsea) are not competing outside what is important for us, the 'fair' Financial Fair Play.
"We are working, thinking and believing that Financial Fair Play is going to be in practice.
"So there are things that are impossible for us (to do)."
Mourinho, whose Chelsea team face City in a crucial top-of-the-table battle on Monday night, speaks from experience after recruiting many players for large sums during his first spell as Chelsea boss at the start of Roman Abramovich's Russian revolution.
When Mourinho first worked in England he admits "it was a free world".
He added: "There was no Financial Fair Play. If your club was a rich one, your owner a rich one, there were no rules. It was an open situation."
It meant Chelsea were unpopular. City, however, are playing a brand of football so scintillating and scoring so freely that they are attracting admirers.
Mourinho said: "In my time we were accused of buying the title, no? Because our owner was Mr Abramovich, just arrived in the country. Maybe now people see City in a different way.
"Times change. Maybe 10 years ago a huge investment in the club was something that people hated and in this moment it's something people accept in a different way.
"Probably, if UEFA goes with Financial Fair Play until the last consequence and they explain really to the people what Financial Fair Play means, maybe in that moment people will realise that some teams are different to other teams.
"But it's something I don't think about at this moment."
Mourinho has long described City, who were beaten 2-1 at Stamford Bridge in October, as favourites for the title and he has claimed Chelsea finishing second in the Premier League this season would be an achievement.
"If we finish second it's fantastic," he said.
"If we finish second doing the formation work, it's an acceleration of our process. If we finish second it's good."
Chelsea will be serious challengers next season, Mourinho has claimed, and need one or two signings, particularly a striker.
City are anticipated to spend big again, with Porto defender Eliaquim Mangala among those strongly linked.
Asked if he would like to buy Mangala, Mourinho said: "We can't. We signed (St Etienne defender Kurt) Zouma, who is even younger and has comparable figures.
"We have the central defender of the Brazil national team (David Luiz), the centre-half of the English national team (Gary Cahill), and the best central defender in the Premier League 2013-14 (John Terry).
"So we're fine (in defence)."
After an injury-ravaged campaign last season under Rafael Benitez, Mourinho did not anticipate his captain would recover top form.
"After the season he had last year, I was not expecting it," said Mourinho, who refused to be drawn on whether Roy Hodgson should take Terry to the World Cup with England.
"I would like to see him playing this way until the end of the season. The World Cup is with him and Roy, not with me."
Terry can expect a busy evening at the Etihad Stadium on Monday against a City side with a 100 per cent record from 11 home games in which they have scored 42 goals.
City beat Manchester United 4-1, Tottenham 6-0 and Arsenal 6-3 at home, but Mourinho is undaunted and determined to challenge the hosts.
"I don't know if other teams simply refuse to attack or they can't do it," Mourinho said.
"Maybe they want to and they can't. I want to attack them. I can tell you that.
"But maybe after 10 minutes or after 20 minutes, people might say I'm not attacking. If I don't, it's because I can't."
Mourinho believes City are "complete", but insists Chelsea's approach will not alter.
He added: "I don't think a lot about them. I'm not going to build my team because they are very good on this or very bad on that.
"I think more about us than them."