Secret documents revealing the extent of the European Central Bank’s knowledge of Greece’s concealed debt issues prior to its €240bn (£195bn) tax-payer funded rescue have been withheld in a “disturbing” EU court ruling.

Internal papers, which detail Greece’s use of complex financial trades to hide its level of debt, were kept from media organisation Bloomberg amid concerns their publication could heighten Europe’s financial crisis.

The three judges presiding over the case at the EU General Court in Luxembourg, in upholding the Bank’s refusal to release the reports, said: “The ECB must be recognized as enjoying a wide discretion for the purpose of determining whether the disclosure of the documents relating to the fields covered by that exception could undermine the public interest.”

Their decision, made on Thursday, has been decried as a sign the European Central Bank (ECB) is becoming less transparent just as it prepares to expand its powers.

Thursday’s ruling came amid calls for increased transparency at the Bank from its own senior members, which take on supervision of all 6,000 euro-area banks from January.