In his remarks, which were recorded on video, Mr. Gudkov also noted that the planned trip to the United States had been used by state-controlled television to accuse him of treason and espionage.

“I just want to say that we need to take a bit more moderate and farsighted approach to our bilateral relations,” Mr. Gudkov said. “Instead of criticizing Putin, we need to help him, to help him fight against Russian corruption because in every interview he emphasizes the importance of fighting corruption. We need to help him to expose the bribers, by providing information on their activities abroad and here in the United States because you know Russian propaganda, Kremlin propaganda, usually use our relations — I mean opposition and America — to discredit us, because we are always being set forth as traitors, as State Department agents, and to destroy our motherland.”

Mr. Gudkov continued, “For instance, when I was in Russia, I heard information spread by the state television that Dmitry Gudkov was going to the United States to sell some secrets and to get new instructions. But if we change our approach, on the one hand, we could show Russian citizens that the opposition acts only according to the interests of Russia. On the other hand, we can demonstrate that the United States helped Russian people to expose Russian corrupt authorities.”

In recent months, the Duma, which is the lower house, has played a growing role as the Kremlin’s political attack machine, adopting laws aimed at suppressing political dissent as well as tightening restrictions on nonprofit groups, particular those receiving support from abroad.

For example, at the Kremlin’s urging the Duma led the charge to enact a ban on adoptions of Russian orphans by American citizens. In recent weeks, there has also been a steady drumbeat aimed at restricting interaction between lawmakers and the West, including legislation to bar officials from owning bank accounts or investments outside Russia.

A letter demanding an investigation of Mr. Gudkov was signed by lawmakers from all the factions in the Duma, including the Communist Party and the nationalist Liberal Democratic Party, whose leader this week called for Mr. Gudkov’s arrest as a traitor.

At a news conference on Friday, Deputy Speaker Sergei Zheleznyak, who is a leader of United Russia, said that Mr. Gudkov’s speech in the United States “demonstrates his disrespect for the requirements set for members of the Russian Parliament, negligence toward his responsibilities as a member of Parliament and a betrayal of national interests.”