Parmalat owes 14.3bn euros ($18bn; £10bn), its auditors say - almost eight times what the company claimed when it went bust in December.
The figures, from accountants PricewaterhouseCoopers, give Parmalat's position as of end-September and exceed even the most pessimistic of estimates.
The stricken Italian food firm declared it was bankrupt after it was forced to reveal a 4bn-euro hole in its accounts.
Its former bosses are being questioned by police, as are senior auditors.
The new numbers issued by Parmalat but calculated by PricewaterhouseCoopers, show that Parmalat's true performance was much worse than it had claimed.
Its core earnings, for example, were 121m euros instead of the 651m it had reported to investors for January-September 2003.
1961: Calisto Tanzi forms Parmalat after inheriting a small family-run food business
1990: Parmalat, now a large food group, listed on the Milan stock exchange
1999: Company sets up subsidiary, Bonlat, in the Cayman Islands
19 December: Bank of America claims a document showing 3.9bn euros in Bonlat's bank account is forged
24 December: Parmalat goes into administration
27 December: Mr Tanzi is taken into police custody
30 December: Mr Tanzi admits the hole in Parmalat's accounts is about 8bn euros but denies ordering any cover up
8 January: Accountants Grant Thornton expel their Italian partner firm because of its involvement in auditing Parmalat
19 January: 11th arrest, that of Franco Gorreri, finance director till 1992 and most recently head of a local savings bank
23 January: Alessandro Bassi, former aide to Fausto Tonna, commits suicide
26 January: Auditors determine that Parmalat's debts are eight times what had been previously thought
Sales for the same period had been 4bn euros instead of the 5.4bn it had claimed, while the full 12 months of 2002 had produced sales of 6.2bn euros instead of 7.7bn.
Still, Parmalat said its Italian operations were seeing sales up almost 15% over the previous year.
Most suppliers, it said, were being paid despite "negligible" cash reserves - although in the US and Brazil "crisis units" were having to be set up to help local managers stay afloat.
The proof that former managers had wildly overstated the firm's performance comes almost exactly a month after Parmalat announced it was going into administration on 27 December.
The company, active in about 30 countries and with 36,000 employees worldwide, had been under investigation by prosecutors since about a week earlier.
The trigger was the discovery that a document purporting to show some 4bn euros held in a Bank of America account by a Cayman Islands subsidiary of Parmalat was a forgery.
That removed the props from a delicate structure of offshore firms and non-existent bond repayments which had been underpinning Parmalat's unexpectedly fragile finances.
Calisto Tanzi, Parmalat's founder, is in hospital with heart trouble, but remains under arrest.
Also under lock and key are former finance director Fausto Tonna. Nine other people including two senior auditors have also been held for questioning.