Corruption has increased in several of the world's best-performing economies as rising growth has encouraged an abuse of power, corruption watchdog Transparency International said Wednesday in its annual report.

"The 2014 Corruption Perceptions Index shows that economic growth is undermined and efforts to stop corruption fade when leaders and high level officials abuse power to appropriate public funds for personal gain," said watchdog chair Jose Ugaz.

Transparency's annual corruption index analyzes the abuse of power, secret dealings and bribery in a country's public sector. High levels of corruption are indicated by a low score.

China, Turkey and Angola were among the most corrupt on the index, despite having recorded an average economic growth of more than 4% over the last four years.

Denmark topped Transparency's index with a score of 92 out of a possible 100, meaning that its public sector is considered to be "very clean." North Korea and Somalia shared last place with an index score of eight.

"Countries at the bottom (of the index) need to adopt radical anti-corruption measures in favour of their people," Ugaz said. "Countries at the top of the index should make sure they don't export corrupt practices to underdeveloped countries."

Afghanistan, which is struggling to end a long-running conflict, was one of the surprises on the corruption index, Afghanistan rose 4 points this year.

China, which is the world's second biggest economy, posted a score of 36 on the index – down four points from last year despite Beijing's launch of a major anti-corruption campaign. Turkey dropped 5 points.

Cote d'Ivoire, Egypt, Saint Vincent, the Grenadines, Jordan, Mali and Swaziland were among the biggest winners in the 2014 index.

There was also good news for nations at the centre of the eurozone crisis, with Portugal, Spain and Italy edging up in the index. Greece made a big jump from the number 89 spot in 2013 to 69 this year.

Germany, Europe's largest economy, retained its 2013 ranking of number 12 in the corruption index, while the US rose by 2 points to the number 17 slot.