An anti-corruption watchdog ranks the U.S. and Germany as the most active at enforcing rules prohibiting multinational companies from using bribes in foreign markets but said Tuesday that half the world's top exporters are doing little or nothing at all to investigate or prosecute offenders.

A new report from Transparency International showed only the U.S., Germany, Britain and Switzerland actively enforced the OECD Anti-Bribery Convention agreed upon by 40 major exporting countries.

Canada fell into the "limited enforcement" category, which is only one notch up from the lowest possible category, which is "little to no enforcement." France, Sweden, Norway and Denmark were also among the countries in this category.

The 1997 Organization for Economic Co-operation and Development convention prohibits bribes to win contracts and licenses, or to dodge taxes and local laws.

At the same time, 20 countries that together account for about 27 per cent of the world's exports, including Group of 20 members Japan, Brazil, South Korea and the Netherlands, showed little or no enforcement, the watchdog said. A further 10 had only limited enforcement — meaning the convention has not had the power it could have, the organization said.

"The 40 countries, which represent more than two-thirds of global exports, would make it very hard to get away with bribery if they lived up to the requirements of the OECD anti-bribery convention," Transparency International head Hugette Labelle said in a statement.

Scant resources for fighting corruption

Italy, Australia, Austria and Finland all showed "moderate enforcement." Convention signatories Colombia, which only joined in 2013, and Iceland, whose share of exports was too small for Transparency's methodology to yield any significant result, were not included.

The report looks at active cases or prosecutions between 2009 and 2012 — a time in which many economies were faltering and the organization noted countries had cut back resources dedicated to fighting bribery.

Transparency said France — which fell into the "limited enforcement" category — reported that it had reduced its number of prosecutors and investigating magistrates by about a third during the time period. The Brussels Court of Appeal, meanwhile, recently said it may be forced to temporarily close because of staffing issues, the report notes.

"In more than half of the parties, there are insufficient resources available to investigate and prosecute foreign bribery," Transparency said.

The organization also called for G20 countries that have not yet signed on to the convention — China, India, Indonesia and Saudi Arabia — to do so promptly.