Cherie Blair used her trip to the G8 Summit in Russia to meet with human rights campaigners.
Mrs Blair was with her husband at the G8 summit in St Petersburg
The prime minister's wife, who is a leading human rights lawyer, privately met the groups at the offices of Human Rights Watch in St Petersburg.
One of the campaigners suggested Mrs Blair had offered to help appeal against a controversial new law.
Tony Blair said he had not discussed his wife's visit with Russian President Vladimir Putin.
"I'm sure the purpose of the visit is simply to indicate the importance we attach to this issue," the prime minister told reporters.
Mr Putin showed his dislike of criticisms about his government's record on human rights over the weekend when questioned by British journalists about the issue.
He took a sideswipe at Mr Blair, saying: "There are also other questions, questions let's say about the fight against corruption.
"We'd be interested in hearing your experience, including how it applies to Lord Levy [Labour's chief fundraiser who was arrested last week]."
Human Rights Watch had raised fears that Mr Putin tried to suppress criticism of his government ahead of the summit by disrupting an opposition conference in Moscow.
And there was controversy about a new law over the financing of foreign groups. Non governmental organisations (NGOs) say it will allow Mr Putin to close down critical organisations.
Maxim Timofeyev, from the Russian legal rights group Civil Control, said they had discussed their concerns about the law with Mrs Blair.
"She said her chambers were ready to help ... to file an appeal with the European Court of Human Rights," he said.
The Russian Government says the law is intended to guard against foreign extremist organisations and secret services.
According to a statement from Human Rights Watch, Mrs Blair said, after her meeting: "I believe passionately that civil society is very much a part of civilised society.
"In all nations we need the expertise, the interest, the passion that NGOs exhibit in whatever particular areas they are interested in."
After talks with rights groups this month, Mr Putin said he would keep watch on how the law was implemented and change it if necessary.
Mrs Blair's meeting comes as the Conservatives call for an investigation into claims that she used her influence to help an acquaintance lobby for NHS contracts.
The Mail on Sunday said Mrs Blair helped Jonathan Metliss, director of a health firm, set up a meeting with the prime minister's health adviser.
Mr Metliss was the boyfriend of a close friend of Mrs Blair, the paper claimed.
Downing Street said there had been a "misunderstanding" and that the adviser set up the meeting himself.