Manchester United manager Sir Alex Ferguson fears the Premier League's new spending controls will be difficult to enforce.
United were one of the driving forces behind the measures agreed yesterday, whereby clubs will not be permitted to rack up losses of more than £105million over three years.
Clubs will also face limits on the amount by which they can increase their total player wage bills - and breaching either measure could lead to points deductions.
Ferguson said however: "It's all good in theory but the application of it will always be difficult. If people have money to burn they can place it anywhere in the world.
"I'll be interested to see how they think they can operate it. It would be good if it was applicable but I have my doubts. I think it's always going to be problem to try to enforce it."
Under the measures, clubs whose total wage bill is more than £52million will only be allowed to increase their wages by £4million per season for the next three years, though that cap does not cover extra money coming in from increases in commercial or matchday income.
Arsenal have also pushed for financial fair play, but Gunners boss Arsene Wenger said he favoured more individual freedom for clubs.
He said: "I personally am for financial fair play in the way that companies and the clubs respect to manage the club with their own resources.
"For the rest I am for freedom, how you use your resources inside the club. I am not in favour of a Brussels-type of society with centralised control with complicated rules. I believe every company should live within its own resources. For the rest, leave it to the company to manage their company how they want to do it.
"It is nonsense because we live in a world where, if you look at Europe, most of the countries are in a very difficult financial position and I believe the minimum we can do in our world is respect the financial balance."
West Ham manager Sam Allardyce said he hoped the new regulations would not lead to the club losing their top players.
He said: "Like everything else it will probably start and we will have some flaws and if they get adjusted and amended as we go along that is fine.
"We will all have to try and live with what the new regulations will be when they are put in place. My only fear, from a personal point of view, is I hope we don't lose our best players."
Aston Villa were one of the clubs understood to have voted against the measures – Saints were one of the others - and their manager Paul Lambert insisted the proposals were still "up in the air".
He added: "Once it is set in stone then people can say whether it's good or bad.
"The Premier League is a vast football league and a business and you can't blame the players.
"Is the money crazy? Yes, it probably is. It's the way football is and the game is, it's not the fault of the players."
Chelsea, to the surprise of some other clubs, did also vote for the regulations and the Blues' manager Rafa Benitez backed that stance.
He said: "If UEFA is doing the same, I think it's good. At the end of the day, you do things in the right way, it will be positive. Stability of the clubs is a key issue.
"The experience in Spain, for example, now with loans and the go to administration and it's a big mess.
"If you can avoid these things then I think it's much better."
Everton manager David Moyes, meanwhile, insisted it was important that the rules did not prevent clubs challenging the status quo.
He said: "We have to have competition. We have to make sure we give everyone the chance to compete. Of course, we don't want overspending - this is the last man and the last club to ask about overspending!
"I don't think it is the right way, but there again, I think we have to be careful that we don't stop people coming into the game who could help to push the game forward.
"I want to be given every opportunity to try to get to the top of the league with Everton. I hope this won't stop me doing that."
Liverpool were also one of the clubs pushing for financial regulation and manager Brendan Rodgers believes it is "a good idea".
He said: "We certainly wouldn't want to see one or two clubs that have a lot more financing than anyone else run away with it.
"We have seen it over the last couple of years - and in particular the last year or so - clubs we would consider to be massive institutions in the game going bankrupt and struggling.
"That is certainly not something we want to see.
"I read something that this club even a few years ago could have gone to the wall because it was struggling financially and that is unheard of at a club like this.
"But it can happen and it is important for the fair play of everyone and the competition itself that there is a playing field we all feel we can compete in.
"Once that kicks in over the next two or three years it will be good for the game."