Greece was the European Union member state that saw the biggest decrease in annual rankings measuring perceptions of corruption across the world.
It dropped three points in a year and is one of five countries in the bloc considered to be more corrupt than it is clean.
Greece is the second worst in the bloc followed by Hungary, Romania and Croatia.
Dr Anna Damaskou, from TI in Greece, said the Novartis scandal — which saw the pharmaceutical company investigated over allegations it bribed public officials — had contributed to the rise in perceptions of corruption.
“The fact there has been no concrete outcome of this case yet means it’s been like a cloud over the country,” she told Euronews.
But, she said, it was important to put the three-point fall into context.
In 2017 the country had seen its score rise due to reforms linked to austerity measures.
At the other end of the scale, Denmark, Finland and Sweden were considered the least corrupt, although all have lost points since five years ago.
“With many democratic institutions under threat across the globe — often by leaders with authoritarian or populist tendencies — we need to do more to strengthen checks and balances and protect citizens’ rights,” said Patricia Moreira, TI's managing director.
“Corruption chips away at democracy to produce a vicious cycle, where corruption undermines democratic institutions and, in turn, weak institutions are less able to control corruption.”