A new study from Deloitte indicates that squad salary levels are more important than one-off transfer fees.

The study also suggests that Premier League clubs' recent lack of European success can be attributed to owners who don't pass on increased revenues to their squads.

"Between 2011-12 and 2015-16 seasons, all European big-five leagues have grown operating revenues [net of transfer proceeds] in excess of total staff costs," the research said.

"Among these, the broadcasting receipts for the period 2013-2016 sent the English Premier League total operating revenues some 76 percent higher, the most dramatic rise among the leagues under analysis.

"All the Premier League clubs, except Chelsea FC, stay in line with the overall results by aggregate figures; Liverpool FC display the highest growth by both metrics, while Manchester City FC have the most positive result.

"Furthermore, Italian champions Juventus FC and French giants Paris Saint- Germain FC also join this cluster of clubs, as their ability to leverage their revenue streams outperforms the increased remuneration of the staff."

The research also shows that Premier League club owners are less likely than rivals elsewhere to use higher revenues from broadcasting and other sources to pay their players more.