The International Monetary Fund (IMF) has admitted making "notable errors" in the design of the 2010 Greek bailout package and in the 2012 debt restructuring plan.

In a confidential document published on June 5 by the United States-based Wall Street Journal, the IMF makes the admission while also laying part of the responsibility at the door of the European Commission and the EU member states, who it claims were too optimistic about Greece's economic outlook.

The Greek bailout package should have been more substantial and should have included debt restructuring from 2010, the IMF now says.