LONDON — The most successful clubs in soccer's richest league have some of the biggest debts in the sport.

A report by British lawmakers last week accused Manchester United, Liverpool and Chelsea — the top three teams in the Premier League — of "financial doping," or reckless borrowing to maintain their domination.

Five of England's 72 lower league clubs have had a minimum of 10 points deducted this season for irregularities stemming from financial problems. Many fans are now worried that the global economic crisis makes it just a matter of time before a Premier League club buckles under.

How did this all come about?

What follows are some questions and answers about the financial problems facing England's top clubs:

Q: Why is there so much money in the top tier of English soccer?

A: The creation of the Premier League in 1992 led to huge increases in television income as satellite broadcaster BSkyB bought exclusive rights to the sport to drive its expansion. The next British broadcast agreement, with Sky and Setanta, is worth 1.782 billion pounds ($2.58 billion) for three years from the start of the 2010-11 season, almost six times more than Sky's initial contract.

Q: So why are clubs borrowing so much?

A: You might say the lure of massive revenue has created massive borrowing. The Premier League generates more income than any other national league through match-day revenue, sponsorship and broadcast agreements, so most clubs are either scared of dropping out of it or desperate to get into it. Three clubs each season are relegated to the far-less lucrative second tier, leading many teams to spend lavishly on player acquisitions and wages to prevent this.

Q: But Manchester United isn't scared of relegation. Why is it so heavily in debt despite its success?

A: England's dominant club of the last 20 years had no debts before being bought by Malcolm Glazer in 2005. The Tampa Bay Buccaneers owner funded his takeover by borrowing money secured against the club's future earnings. With the loans set at relatively high interest rates, the club's "healthy operating profits ... are more than eaten up by the servicing of its debt," according to a report by British legislators.

Q: Why did Glazer borrow so much?

A: Glazer simply believed that United was not exploiting its commercial potential and that the club could make enough money in the long term to justify his risk. Glazer has increased United's turnover through commercial activities, sponsorships and higher ticket prices. Regular preseason tours to overseas markets such as Asia and the United States have also helped raise profile and income, but probably not to a level that has reduced debt as much as the Glazers hoped. After winning the Champions League and Premier League last season, United posted pretax losses of $65.2 million. Interest and repayments on debt of $945 million took $66.2 million annually out of United's profits.

Q: What about Liverpool and Chelsea?

A: Tom Hicks, owner of MLB's Texas Rangers and the NHL's Dallas Stars, and George Gillett Jr., owner of the NHL's Montreal Canadiens, bought Liverpool for $430.8 million in 2007, apparently for the same reasons that Glazer bought United. Liverpool's debt has swelled to $509.5 million because of the financing of the takeover. Chelsea is in a slightly different position. Roman Abramovich owns the west London club and furnished it with huge interest-free loans from his personal fortune. That means Chelsea is not at risk from creditors, but would be hugely vulnerable if Abramovich ended his involvement. The club was reportedly hours from going out of business before the Russian oligarch bought it in 2003.

Q: Could the same thing happen to more clubs?

A: Yes. Under British financial regulation, investors who build up a stake of 30 percent of the voting rights in a publicly traded club are required to make a takeover bid. This is exactly what Glazer did, allowing him to remove United from the London Stock Exchange and take it into private ownership, and what Arsenal board members feared Russian businessman Alisher Usmanov was trying to do in October 2007. So they signed an agreement not to sell any shares to anyone seen to have a predatory interest in the north London club, which is listed on the junior exchange Plus Markets. Clubs that are privately held can be sold to anyone at any time if the price is right.

Q: So is Arsenal safe from a takeover?

A: Not necessarily. A subsequent agreement lasting until October 2012 means board members can only sell their shares to another person if the other parties to the agreement do not wish to buy them. But that applies to board members only. Nina Bracewell-Smith is an interesting story because she was forced off the board in December and could be willing to sell her 15.9 percent stake. Usmanov already owns more than 25 percent of the club, with American Stan Kroenke, who controls the NBA's Denver Nuggets, the NHL's Colorado Avalanche and MLS's Colorado Rapids, the largest shareholder on Arsenal's board at 20.5 percent.

Q: How much would a club like Arsenal cost?

A: Kroenke paid $60.3 million last month for 8.1 percent of the club. That would make the whole club worth $760 million.

Q: What happens if club debt becomes unsustainable?

A: Short-term, teams under pressure could be forced to sell players to raise funds and reduce outlay on wages, which rose to an average 63 percent of turnover for 2006-07 — the last full season for which figures are available. Mid-table West Ham looks likely to be forced to do this in the offseason after its Icelandic owner, Bjorgolfur Gudmundsson, went bankrupt, while relegated teams habitually shed players. If things got really serious and clubs defaulted on debt, creditors could end up owning the clubs.

Q: What would happen next?

A: There are several cautionary examples of what could be called "financial doping" littering English soccer history. The record for the costliest player in Britain was broken 10 times between 1922 and 1950, four times by the Sunderland club nicknamed "The Bank of England" for its wealth. But the team was implicated in a major financial scandal in 1957 when it was hit with a huge fine for breaking the maximum wage that governed English soccer. The following year, Sunderland was relegated from the top tier for the first time in 68 years of league play. The club has won just one major trophy since.