Two weeks before Russia holds a general election, the government has added the Levada Center polling organisation to the list of “foreign agents” for receiving funds from overseas, ramping up pressure on one of the country’s last independent sources of data on public opinion.

The pollster’s director Lev Gudkov told the Dozhd television network that the move will make it impossible for Levada to continue operating and it will likely have to close down as it is unable to appeal the justice ministry’s decision. The ministry added Levada to the “foreign agent” list after claims in July by pro-Kremlin activists that it received more than $120,000 from the US government since 2012.

One of Russia’s three largest national polling agencies, Levada is now barred from participating in any kind of activity in election campaigns, effectively muzzling it ahead of the parliamentary elections scheduled for September 18.

The move comes four days after Levada reported a sharp decline in support for the ruling United Russia party. The centre's August poll said that among those who intend to vote this month the party's rating slid from 57% to 51%. It also reported that around half of Russians expect the elections to be rigged in some way. Other recent polls that do not sit well with Kremlin foreign policy included a report in August that one in two Russians do not agree with destroying imported food that is confiscated under counter measures to Western sanctions.

The justice ministry’s move clouds hopes that United Russia's dominance of the political landscape will allow the elections to the State Duma lower house to be more free from ballot stuffing and other violations of electoral law than earlier elections.

Coming amid a broader crackdown on civil society thought to have been ordered by President Vladimir Putin, the adoption of the “foreign agent” law has hobbled most of the country’s non-governmental groups engaged in political work. Under the legislation the government can demand additional audits and probes of groups defined as foreign agents and ban them from doing work it defines as political.

The addition of Levada to the “foreign agent” list was also unexpected because it is not the only pollster to record falling support for United Russia. The Russian Public Opinion Research Centre (VCIOM) and FOM both recently noted a significant slide in support among the general population.