The United States is facing criticism after it removed Cuba and Malaysia from the US State Department’s list of the countries categorically failing to respond to widespread human trafficking.

Both countries have been upgraded from tier 3 in the 2015 Trafficking in Persons report, the worst ranking given by State Department’s annual overview of the actions taken by countries across the world to tackle modern slavery and trafficking.

Anti-trafficking groups have expressed concern at the “transparent” political motivations of this year’s rankings, which they claim call the integrity and impartiality of the report into question.

“We are very surprised by this year’s report, which seems to be making blatantly political decisions that we consider will have a really detrimental impact on both the integrity of the report and progress in the global fight to end modern slavery,” says Melysa Sperber, director of the Alliance to End Slavery and Trafficking (Atest).

“The TiP report can be a really valuable tool in holding governments to account and can have a tangibly positive influence in changing things on the ground and there is a real import in maintaining its credibility.”

The report, which has been published since 2001, is the principal diplomatic tool with which the US engages foreign governments on human trafficking. Under US law, those countries on tier 3 could trigger non-trade related sanctions, leading to restrictions on US foreign assistance and access to global financial institutions such as the World Bank.

After 12 years on tier 3, Cuba’s sudden upgrade to the tier 2 watch list comes fast on the heels of the re-opening of the US embassy in Havana and the re-establishment of diplomatic relations after a half-century of estrangement.

Last year’s TiP report contained criticism of Cuba’s trafficking record, including allegations of child prostitution and forced labour by the Cuban government.

In an interview following the leaking of the proposed upgrade last week, Senator Robert Menendez, a Democrat on the Senate Foreign Relations Committee, said he saw the move as politically motivated.

“You have to earn your way up the ladder, not just have political expediency be the reason that you get moved from tier 3,” he said.

The US State Department insists that the upgrade is based on better cooperation between Washington and Havana on eradicating human trafficking and ensuring better protection of victims and the Cuban government taking a more open and proactive approach to sharing information and on the prosecutions of traffickers.

Malaysia was also given an upgrade to the tier 2 watch list after a year on tier 3. It comes as President Obama works to smooth the way for the Trans-Pacific Partnership, a huge US-led free trade deal with Malaysia and 11 other countries across south-east Asia. Malaysia’s upgrade removes a potential barrier to getting the trade deal finalised, as countries on tier 3 are theoretically barred from fast-tracked trade deals.

Over the past year Malaysia has been accused of widespread forced labour in its electronics industry, an industry used by major global electronics brands such as Samsung, Sony and Apple. It has also faced allegations of forced labour and trafficking in its palm oil industry.

The upgrade also follows international outcry over the discovery of 139 graves in jungle trafficking camps near the border with Thailand, used to hold thousands of stateless Rohingya migrants to ransom. The US State Department said that the discovery of the camps happened after the cut-off for evidence-gathering for the TiP report.

“We are disappointed in the extreme,” says Aidan McQuade, director of Anti-Slavery International.

“Abysmal forced labour on the scale we see in Malaysia, Qatar and Uzbekistan does not exist without fundamental failures in government and it’s unfortunate that American interests seem to be diluting this message rather than holding governments to account and so transparently putting trade and political interests over human rights. What we are seeing here is one of the most important diplomatic instruments in the struggle against slavery being compromised.”

In the report, the US State Department said that while the government of Malaysia does not fully comply with its minimum standards for the elimination of trafficking, it is making significant efforts to do so.

“In 2014, the government consulted with civil society stakeholders to draft and propose amendments strengthening the existing anti-trafficking law and addressing concerns raised in previous Trafficking in Persons reports, including by allowing trafficking victims to move freely and work, and for NGOs to run the facilities,” the report says.

Uzbekistan has also been upgraded from tier 3 to the tier 2 watch list, despite continuing concerns over its use of state-sanctioned forced labour in its annual cotton harvest.

Thailand, also relegated in 2014, has remained on tier 3 this year, despite concerted lobbying from the Thai government for an upgrade.

Last year a Guardian investigation revealed slavery in the supply chain of farmed Thai shrimp sold in supermarkets across the world. This month a follow-up investigation also revealed that Rohingya migrants held prisoner in a network of trafficking camps in southern Thailand were being sold on to Thai fishing boats and that Thai fishermen have been actively facilitating the trafficking rings exploiting hundreds of thousands of Rohingya migrants attempting to make the crossing into Malaysia.

Qatar remains on the tier 2 watch list for the second year running. According to TiP policy, countries can remain on the tier 2 watch list for three years before an automatic relegation to tier 3.

The US State Department’s Office to Monitor and Combat Trafficking in Persons, which produces the TiP report, has been beset by a leadership vaccuum after the sudden departure of Ambassador Lou CdeBaca last year. President Obama only confirmed Susan Coppedge, a former assistant US State Attorney, as his replacement last week.

Launching the report, the US Secretary of State, John Kerry, said, “The bottom line is that this is no time for complacency. Right now, across the globe, victims of human trafficking are daring to imagine the possibility of escape, the chance for a life without fear, and the opportunity to earn a living wage. I echo the words of President Obama and say to them: ‘We hear you, and we will do all we can to make that dream come true.’”