Political parties are viewed as the institutions most affected by corruption in the State
Ireland has been ranked as the 18th least corrupt state in the world - falling one spot from its previous ranking.
Nordic countries dominate the top of the list, with Denmark in first place followed by Finland and Sweden. The UK and Germany also make the top 10.
Ireland ties with Hong Kong and Japan and is sandwiched between the US and Austria in joint 16th and Uruguay in 21st - which is followed by Qatar in 22nd.
The breakdown for Ireland shows that the perceived corruption of political parties is 4.4 out of 5, Parliament and Legislature scores 4/5, while perceived corruption in religious bodies is 3.9/5.
The report notes that a number of European countries need to take action to fight corruption:
"Corruption remains a huge challenge across the region, often going hand in hand with repression. In low-scorers Hungary, Poland and Turkey (which has plummeted in recent years along with Spain) politicians and their cronies are increasingly hijacking state institutions to shore up power," the report says.
It adds that there is a "worrying trend" in the Balkans and that Azerbaijan, Kazakhstan, Russia, Ukraine and Uzbekistan all score poorly and face governments who have been slow to move on anti-corruption reforms.
Somalia is ranked as the joint-most corrupt country with North Korea - they come behind Afghanistan and Sudan.
Transparency International chair, Jose Ugaz says that "The 2015 Corruption Perceptions Index clearly shows that corruption remains a blight around the world."
He continues, "But 2015 was also a year when people again took to the streets to protest corruption. People across the globe sent a strong signal to those in power: it is time to tackle grand corruption."