Portugal's main opposition party on Sunday took aim at centre-right Prime Minister Pedro Passos Coelho over a report that he failed to pay his social security contributions for five years.
The Publico daily reported Saturday that Passos Coelho had failed to make his contributions between 1999- 2004 while he was a consultant for vocational training company Tecnoforma.
The prime minister said in a statement that he had never been notified of "a Social Security debt", for the period in question.
According to the newspaper report, the prime ministers had decided voluntarily to pay the outstanding amount in February to avoid "unfounded accusations".
However that was not enough to pacify the opposition.
The head of government "needs to give a clear explanation to the Portuguese people," because "he cannot say that he was ignorant of the law," said Ana Catarina Mendes, vice-president of the Socialist Party, the main parliamentary opposition.
It is not acceptable for a prime minister to apply different rules for himself "while requiring more rigour in debt payments from others than he applies to himself," she added.
Left Bloc party spokeswoman Catarina Martins said that the prime minister's actions "won't surprise anybody" at a time when ordinary people are remortgaging their houses because they can't pay their debts.
Social Security Minister Pedro Mota Soares however said that Passos Coelho "had been the victim of administrative errors".