Financial Fair Play (FFP) architect and former Belgian prime minister Jean-Luc Dehaene has died at the age of 73 following a reported fall in France.
Dehaene, who had been diagnosed with cancer, had been instrumental in setting up FFP as chairman of Uefa's Financial Control Panel.
He envisaged the rules as a a way of controlling football clubs' spending and encouraging financial responsibilty.
He had recently investigated the finances of newly-crowned Premier League champions Manchester City and French league winner Paris St Germain.
Both clubs are owned by Abu Dhabi and Qatari investors respectively and have been the benefactors of hundreds of millions of lucrative sponsorship deals.
City were reportedly about to be hit with a £50 million fine for breaching FFP's rules but it has since emerged the club has not yet reached a settlement with Uefa over the proposed sanctions.
Dehaene's death is expected to further delay the announcement of City's punishment.
Speaking of his appointment to the panel in 2009, Mr. Dehaene said: "The rule of financial fair play is aimed at ensuring the healthy, lasting viability of clubs. By imposing this rule on all clubs participating in European competitions, Uefa has taken the path both the European Commission and Parliament had hoped for.
"By agreeing to chair the Club Financial Control Panel, I hope to be able to help achieve this ambitious objective, which is vital to the future of European football."
Before his involvement with Uefa, Dehaene was Belgian PM from 1992 until 1999 and had been involved in brokering an EU constitution, many parts of which were adopted in the Lisbon Treaty.