According to the Portuguese central bank, in the second half of 2017, in Portugal, 9,760 counterfeit notes were withdrawn from circulation, 1,679 more than in the first half of 2017.

The 20-euro note is the most often counterfeited, with 5,223 notes withdrawn from circulation, followed by 50 euros with 2,092 notes.

The banking regulator said the "[seized notes] remain residual when compared to banknotes in circulation."

According to a statement issued by the European Central Bank (ECB), also published on the Bank of Portugal website on the second half of 2017, some 363,000 counterfeit euro banknotes were withdrawn from circulation, an increase of 9.7% over the first half of 2016 and 2.8% year on year.

The 20- and 50-euro banknotes accounted for around 85% of forgeries and the majority (97.8%) of counterfeit notes were detected in Euro Zone countries. Around 2.3% of notes were seized in member states of the European Union and 1% were detected in other parts of the world.

According to the ECB, the probability of receiving a counterfeit euro banknote is now small and so it is a "safe and reliable" method of payment.

In 2017 the increase in the amount and value of genuine euro banknotes in circulation was around 5.9% and 4.0%, respectively.

More than 21 billion euro banknotes are currently in circulation, with a total value of more than €1.1 billion, the ECB said.