Portugal saw the highest increases in tax burdens on personal income in 2013, according to figures released on Friday by the Organisation for Economic Co-operation and Development (OECD).

According to the report, personal income tax has risen in 25 out of 34 OECD countries in the past three years.

The Paris-based OECD said the burden had been highest in Portugal due to statutory rates, and was followed by the Slovak Republic due to higher social security contributions, and the United States due to expiry of previous reductions in employee social security contributions.

Portugal has had to cut spending and impose harsh austerity to meet the targets set in its 78-billion-euro (about 108 billion U.S. dollars) bailout agreement it signed with the international lenders of troika, namely the European Union, the International Monetary Fund and the European Central Bank in May 2011.

Personal income tax rise has been held to strong scrutiny in Portugal and has led to constant anti-austerity protests across the country.

Portugal saw tax rise 41.1 percent of GDP in 2013, 3.5 percentage points higher than the previous year and 4.6 percentage points higher than in 2009.

Tax on employment incomes increased on average by 0.2 percentage point across the OECD to 35.9 percent. While it increased in 21 out of 34 countries, it fell in 12 and remained the same in one, according to the report. Endi