In excess of â‚¬5bn is placed annually in illegal bets in Greece according to the general secretary for transparency Giorgos Sourlas, who is calling for a heavy clampdown on illicit gambling activities.
The news follows warnings last month by Evenios Giannakopoulos, chief of regulators the Hellenic Gaming Commission, that legal betting in the economically-troubled nation has taken a downturn.
Giannakopoulos said in an interview with Kathimerini newspaper that turnover has fallen approximately 37% - from â‚¬8.7bn in 2009 to â‚¬5.5bn last year - and gross profits have dropped from â‚¬2.5bn to â‚¬1.5bn. He estimated that a turnover of â‚¬4-5bn and profits of â‚¬1.5bn are generated annually by 60,000-100,000 illegal gambling machines instead.
This does not include unauthorised online gambling which has a turnover of about â‚¬1bn, Giannakopoulos added.
Sourlas agreed in a meeting on Tuesday with public order minister Vassilis Kikilias that at least â‚¬5bn per year is generated by illegitimate gambling operations, "harming the national economy and acting as a money laundering mechanism for ill-gotten gains".
Sourlas told the minister that during consultations with Giannakopoulos he had been assured that measures were being put in place and that he was "optimistic that an end will be put to organised crime rings operating without constraint".
Cyprus also wants to bolster its armoury against illegal gambling operations with a recently proposed bill that would broaden police powers.
The new legislation, which is currently being discussed in parliament, would allow police to shut down venues suspected of illicit gambling activities until the case could be tried by a court and introduce stricter penalties including five years in jail and fines of up to â‚¬300,000.
AKEL MP Yiannos Lamaris, the house interior affairs committee chairman, said that current legislation made it difficult for authorities to prove the illegal use of gambling machines.
It is common for police to raid an establishment and seize all the equipment only for it to open the next day with new machines.
With the power to secure an injunction suspending the operation of a venue, Lamaris said it will be much easier for the authorities to stamp out illegal gambling.
Politicians expect the new legislation will be passed by parliament before the summer recess.