A European delegation on a two-day visit to Cambodia warned on Tuesday that a deterioration in the country’s human rights situation could affect European Union aid and trade preferences, both of which provide substantial economic benefits to Cambodia, according to a statement released at the end of their visit.

The warning, although vague, was one of the strongest statements to date by one of Cambodia’s donors over the unfolding political crisis in the country, which has seen the opposition leader jailed and his party under threat of imminent dissolution over charges of treason that human rights groups say are trumped-up.

Werner Langen, a member of the European Parliament who led the six-person delegation on a two-day visit to Phnom Penh this week, said in Tuesday’s statement that Cambodia needs “an open and transparent level playing field” in order to guarantee free and fair elections next year. The EU, along with Japan, has in recent years been one of the top donors to Cambodia’s electoral process and electoral reform.

“The government of Cambodia should be aware that the European Parliament is a co-legislator for budgetary and trade issues,” Langen said. “A serious deterioration of the human rights situation might have implications for development assistance programmes and trade preferences.”

He also called on the government to release the opposition leader, Kem Sokha, to halt the process of dissolving the Cambodia National Rescue Party, and to restore a free space for political parties, media outlets, and civil society organizations, all of which have come under threat in the recent crackdown.

The statement follows a warning from the Swedish government last month that the country would consider downgrading its relations with Cambodia in light of the political situation.

The European Union is one of Cambodia’s most significant foreign donors, as well as one of the top destinations for Cambodia-made garments and other exports, such as sugar, under the Everything But Arms trade preference scheme, which provides duty-free and quota-free access to European markets for developing countries.

According to Commerce Ministry and EU statistics, Cambodia exported around $4 billion in goods to the EU in 2016, mostly garments, accounting for around 40 percent of the country’s total exports. The EU and its member states also gave over $150 million in aid in 2015.

The delegates visiting Cambodia were all members of the European Parliament’s ASEAN Delegation. They met on Monday and Tuesday with officials at the Ministry of Commerce and the Ministry of Foreign Affairs, as well as with civil society organizations and the National Election Committee, which the EU has helped fund.

After meeting with the delegates on Tuesday, ruling party lawmaker Chheang Vun told reporters that the EU parliamentarians expressed concern about the arrest of Kem Sokha and potential dissolution of the opposition party. He said he explained to the delegates that Kem Sokha was arrested because he had committed a crime by receiving funding from abroad and causing social instability.

According to a statement released on Monday, Foreign Minister Prak Sokhon also met the delegates and told them that the current political situation was in accordance with the democratic process and that NGOs and newspapers had only been targeted due to their violations of the law.

“The closure of The Cambodia Daily newspaper and NDI and the case of the detained opposition leader were measures carried out in accordance with applicable law, aimed at strengthening the rule of law and defending independence and sovereignty against attempts to interfere in internal affairs and overthrow the government.”