MADRID, July 10 (Reuters) - Troubled Spanish fishing firm Pescanova PVA.MC , which filed for insolvency in April, had net debt of 3.3 billion euros ($4.2 billion) at the end of December, the company said in a statement, citing an audit report carried out by KPMG. This is more than double the 1.5 billion euro debt mentioned in the company's insolvency filing. The former management of Pescanova acted to conceal the company's true debt position for many years, the firm said, citing the audit. ($1 = 0.7778 euros) (Reporting By Sonya Dowsett; Editing by Julien Toyer) ((sonya.dowsett@thomsonreuters.com)(+ 34 91 585 8328)(Reuters Messaging: sonya.dowsett.thomsonreuters.com@reuters.net)) Keywords: PESCANOVA/