Bolton Wanderers have admitted their debts have grown to a staggering £163.8m, with £50.7m haemorrhaging during the 12 months to June 2013. It raises fears that the club may follow Leeds United and Portsmouth into financial crisis.

Only Chelsea – who announced a yearly loss of £49.4m to take them back into the red after making a small profit the previous year – Manchester United and Fulham have a greater debt than Bolton, yet the north-west club is the only one of these outside the Premier League. The eye-watering loss in a single year means Wanderers have the unwanted distinction of becoming the fifth club to have lost more than £50m over 12 months. Yet as Manchester City, who have done it four times, Chelsea (seven), Liverpool and Aston Villa (once each) all boast far greater financing and revenue streams than Bolton, their ability to soak up such astronomical losses will be questioned.

In a statement Phil Gartside, Bolton's chairman, said: "This year's results show the difficulties faced in the football business when a club has enjoyed a sustained and successful period in the Premier League – in our case 11 years – then suffers relegation to the Football League Championship. The ever-widening gap between the two leagues makes the transition extremely difficult, even with the benefit of parachute payments."

The club's perilous finances underline the dangers of overspending and dropping out of the Premier League as Wanderers did in May 2012. Concerns are heightened by their being dependent on a single benefactor, the owner Eddie Davies. Sources at Bolton say Davies, who took over Wanderers for £2.5m in 2003, has no plans to walk away and that there is a five-year plan to ensure finances will return to a less fraught condition, which does not depend on rejoining the Premier League. Yet as £151.3m of the debt is owed to Davies through his company, Moonlight Investment Ltd, the future of Wanderers is within his compass.

Gartside conceded the club's future hinges on Davies' continuing goodwill while admitting that financial fair play rules mean he can no longer support the club as before. "It should go without saying that Eddie Davies continues to provide a humbling level of support to the club," Gartside said.

"However, [owners'] financial support is no longer possible in this league without severe penalty. We are responding to a changing environment … by development of the wider Burnden Leisure business interests. This year we secured sole ownership of the hotel, expanded our education business and applied for planning permission to increase our non-football operations.

"We will continue to invest, both in the long and short term, where the returns can be justified. However, financial fair play rules require an alternative funding structure and Bolton Wanderers is very much moving towards a self-sustainable future."

Bolton's relegation took place the year before the new Premier League television deal, worth a record £3bn over three seasons.

Davies's decision to charge interest on loans to the club will be questioned. Although he ended the policy in July, Mohamed Al Fayed, for example, never charged interest on loans that left Fulham £193m in debt. Fayed sold Fulham to Shahid Khan last summer.