Russia's lower house of parliament on Friday approved a bill that brands as "foreign agents" non-governmental organisations who receive funding from abroad.
The legislation, condemned by the European Union and Washington, was passed by the State Duma with 374 votes in favour, three against and one abstention in the final reading.
A breach of law would be punishable by hefty fines or jail time. The deputies also passed a law making libel a criminal offence punishable by a fine of up to 5 million rubles ($152,000), voting 238 in favour to 91 against.
Communist lawmakers staged a walkout. Putin has accused the US State Department of funding the winter protests that erupted against his return for a third term.
Ponomarev, of the A Just Russia faction, said the bill made him a foreign agent because he had taken foreign donations to help last week's flood victims.