Washington (CNN) A main proponent of the Russia sanctions law known as the Magnitsky Act says Natalia Veselnitskaya, the Russian lawyer who met with Trump campaign associates in 2016, is "a full-on agent" of Moscow.

Bill Browder, a Vladimir Putin critic who pursued the sanctions law after the suspicious death of his lawyer, Sergei Magnitsky, in a Russian prison, told CNN's Erin Burnett on Friday that Veselnitskaya's statement in an interview with NBC News that she was a Russian informant is "sort of only halfway there."

"She was an agent of the Russian government," asserted Browder, who has said Veselnitskaya has been trying to overturn the sanctions law. "She's an agent of Vladimir Putin, and when she went to Trump Tower, she went there on behalf of Vladimir Putin."

Browder, who is the CEO of Hermitage Capital Management, also alleged that Veselnitskaya "lies a lot."

"In this particular case, I think she thinks by calling herself an informant is less damning than when the truth finally comes out about this whole thing, which is that she's a full-on agent," he said.

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