Around four in 10 medals at the Rio Olympics are being won by countries with moderate to high levels of perceived corruption.
Among those rated as highly corrupt are North Korea, which had six medals after nine days of competition, Uzbekistan (five medals) and Venezuela (one).
China (45 medals) and Russia (30) also have significant levels of perceived corruption.
The Press Association analysed the results from Rio using the Corruption Perceptions Index, compiled each year by the non-governmental organisation Transparency International.
The index ranks countries on a scale of zero (highly corrupt) to 100 (very clean), based on surveys and assessments of public sector corruption.
PA figures show that just under 40% of medals handed out in Rio so far have gone to countries with a corruption score of between zero and 50 - towards the "highly corrupt" end of the scale.
Transparency International gives China a score of 37, Russia 29 and North Korea eight.
At the other end of the scale, countries in the least corrupt quarter of the index - a score of between 76 and 100 - have won just over 40% of medals.
Top of the list is Denmark, which has a score of 91 and has seven medals so far. The UK, which has 38 medals to date, is also in the "cleanest" quarter of the corruption index with a score of 81.
The country with the most number of medals at Rio, the United States, has a score of 76.