The number of NHS foundation trusts in deficit has almost doubled as financial pressures on the health service take their toll.
Regulator Monitor said 40 foundation trusts ended the last financial year in the red compared to 21 in 2013.
The combined deficit of the 40 trusts was £307 million compared to £190m the year before.
Among those which have plunged into debt is the Barnsley Hospital NHS trust, where an investigation is ongoing to calculate the scale of the deficit estimated to be at least £7.4m. The Rotherham NHS trust also posted another year of losses but is expected to return to the black in 2014-15.
A spokesman said that 22 organisations in deficit are already subject to regulatory action or investigation by Monitor and account for 70 per cent of the overall deficit.
But the figures also showed there was an overall surplus when all foundation trusts were taken together, suggesting a widening gap between those with sound finances and those that are struggling.
Overall the foundation trust sector made a surplus of £133m in 2013-14. But Monitor said that this was a “significant decline” compared to the previous year - when there was a £491m surplus.
It said there were signs of “increased pressures upon services” as a number of trusts failed to meet waiting times targets in the final quarter of the year.
“The majority of patients attending foundation trusts are receiving quality services in very difficult financial circumstances,” said Jason Dorsett, finance and reporting director at Monitor.
“Times are tough and hard decisions will have to be made to ensure patients continue to get the services they need at an affordable cost to the taxpayer. However, many trusts are taking positive steps such as increasing frontline staff to tackle the challenges they are facing.”
Figures showed foundation trusts hired an extra 24,000 members of staff last year to upgrade services in the wake of the report into the Mid Staffordshire scandal. Most of these were nursing staff.
A Department of Health spokeswoman said: “We understand some trusts are facing financial challenges this year but it is essential that trust CEOs have a tight financial grip and ensure they live within their means. Delivering high-quality services and balancing the books must go hand in hand.”