Thousands of Portuguese demonstrated against the government's tough austerity measures in a biggest ever protest since the beginning of this year in downton Lisbon Saturday.

The demonstration was organized by the General Confederation of Portuguese Workers (CGTP).

Raising high placards the protesters marched over one kilometer from Principe Real to the Municipal Square, chanting slogans.

The angery mass complained that the Portuguese government's austerity measures have caused high rate of unemployment, the reduction in education investment, pension and healthcare insurance as well as the increase in daily life costs including rent, warter and electricity bills.

According to the data released recently by Portugal's National Statistic Institute (INE), the country's gross domestic product (GDP) shrank by 3.2 percent in 2012, more than that had been expected.

The troika comprising the European Union, the International Monetary Fund and the European Central Bank, which have granted Portugal a bailout of 78 billion euros (about 103 billion U.S. dollars) had forecast an economic contraction of 3 percent for the country in 2012.

The INE also said that Portugal's unemployment rate rose to a record 16.9 percent in the fourth quarter last year. A total of 923,200 Portuguese were out of work in the end of last year.

To meet the requirements of the troika, the Portuguese government is impelementing harsh austerity measures and economic reforms for the bailout which have caused widespread protests throughout the country since September last year.

The Portuguese Bank forcast in its lastest economic report issued in January that Portugal's GDP will shrink 1.9 percent in 2013 and its economy will see a moderate recovery with 1.3-percent growth in 2014.