"We are going to make a revision of ticket prices, which will make ticketing free all day Sunday and on public holidays for residents in Portugal - the Portuguese and foreigners living in Portugal - but tourists will pay on Sunday and on public holidays," said Pedro Adão e Silva on Wednesday evening during the "Grande Entrevista" programme on RTP3.

Currently, entry is free on Sundays and public holidays, during the morning, for everyone.

Pedro Adão e Silva said that "70 percent of visitors to Portuguese museums are foreigners" and, of the 30 percent of Portuguese visitors, "only 15 percent pay full ticket, everything else has great discounts, from 50 to 60 percent".

"We can, with this kind of change, have a great effect on revenue", he defended.