Firms doing business with the giant economies of China and India should tread carefully.

Foreign companies run an "extreme risk" of being linked to modern forms of slavery in both countries, according to a new report from Verisk Maplecroft, a subsidiary of Verisk Analytics (VRSK).

"Companies are heavily reliant on goods and raw materials from India and China," the risk consultancy said. "However, sourcing from these countries can come with a substantial risk of association with forced labor."

Verisk researchers have compiled a new index ranking 198 countries around the globe based on the level of risk that businesses will be exposed to "slavery, servitude, trafficking in persons and forced or compulsory labor."

North Korea, notorious for its use of prison labor camps, tops the list of worst offenders, followed by South Sudan and Sudan. India (15th) and China (23rd) are the highest ranked major economies.

Related: U.S. steps up pressure on China over prison labor

The report warns of forced labor in India's agricultural and garment sectors, as well as the exploitation of children in mining. In China, the researchers say, forced labor is used across multiple industries, including electronics and mining.

And they report similar risks across many other Asian markets.

The Indian and Chinese governments didn't respond to requests for comment on the study on Thursday.

The sheer number of places around the world where businesses run a serious risk of exposure to slavery is startling. Verisk Maplecroft rates 115 countries as high or extreme risk, including more than 80% of sub-Saharan African nations.

And even the U.S. and the European Union aren't seen as safe havens: they're both considered medium risk.

"When countries with the most advanced legislation struggle to completely eradicate slavery, it reveals the challenges governments in less developed regions face," said Alex Channer, Verisk Maplecroft's principal human rights analyst.

In compiling the index, the researchers looked at countries' legislation, law enforcement and reported evidence of abuses.