"We took a loan that was to be repaid in 2019," he said in a telephone interview. "It was public. I know that what we've done then was consistent with what was done by many euro zone countries."
A subsequent government extended the deal's maturity to 2037, he added.
Apart from Goldman Sachs ,JP Morgan and Morgan Stanleyalso intermediated such transactions in Greece, according to Papantoniou.
Goldman Sachs officials declined to comment as did Morgan Stanley. JP Morgan officials were not immediately available for comment.
Italy, France and Spain were among the euro zone members doing such swaps at the time, he added. Eurostat, the European Union's statistics office, has asked Greece for explanations on these debt swaps by Feb. 19.
These types of debt swaps are destabilizing financial markets and the European Commission should thoroughly investigate the case, Simon Johnson, Professor of Entrepreneurship at MIT Sloan School of Management, told CNBC.com Tuesday.
The transactions allowed countries to buy the currency at historical rates, which were lower, and record the debt for statistical purposes at the stronger market rate, thus making the debt look smaller. Eurostat banned this way of registering debt in 2008.
These and other transactions, while not illegal, have come under increasing scrutiny. Critics say the moves masked growing debt loads and impending financial problems (Read more here).
Papantoniou said the current fuss around the transactions surprised him. "It's completely crazy," he said, adding that Greece came into the limelight on this "because of the crisis and because of the stereotype that Greece has cheated on its statistics."