Martina Navratilova, the nine-time Wimbledon champion, has regained her Czech nationality after saying she was "ashamed" of George Bush.

Speaking to reporters in Tokyo, where she is due to play in an exhibition tournament, Navratilova confirmed she had again become a citizen of the country of her birth, 33 years after she fled communist Czechoslovakia to live in the US.

"I lost [Czech citizenship] at the time I defected. I got it back on February 9," she said, adding that she had decided to retain her US nationality.

In an interview last year with a Czech newspaper, Lidove Noviny, the tennis player said she was as ashamed of the US under Bush as she once was about Czechoslovakia, which split into the Czech Republic and Slovakia after communism fell in 1993.

"The thing is that we elected Bush," she said. "That is worse! Against that, nobody chose a communist government in Czechoslovakia."

Navratilova was 18 when she fled to the US, angering the communist Czech regime, which immediately stripped her of her nationality. She became an American citizen in 1981. She later said she had been forced to leave Czechoslovakia because the authorities were trying to stop her from playing in the US, where the majority of big tournaments were then held.

She had little cause to regret that decision. She went on to become one of the most successful players of all time, winning 18 grand slam singles titles, including nine Wimbledon crowns, and 31 grand slam doubles titles. Her natural strength and obsession with physical fitness helped prolong her career well beyond the length of most athletes.

Navratilova retired in 1994 but re-emerged six years later to win several doubles tournaments. She played her last competitive match in 2006, capturing the mixed doubles title at the US Open, the 354th tournament of her career.

Since retiring, the outspoken 51-year-old has commentated for the BBC and the Tennis Channel, but devotes much of her time to charitable and political causes. She has worked for People for Ethical Treatment of Animals and underprivileged children and campaigned for gay and lesbian rights.

She is currently a fitness and health ambassador for the AARP, an advocacy group for the over-50s that has more than 39 million members, and plans to open a tennis academy for youngsters in the Czech Republic.

Navratilova first indicated she was unhappy with the Bush administration's position on gay and lesbian rights in a 2002 interview on CNN's Connie Chung Tonight show.

Asked why she had told a German newspaper that she felt as if she had changed "one system that suppresses free opinion for another", Navratilova said that, as a lesbian, life was harder in the US than in Europe.

Accused by Chung of being "un-American", Navratilova responded: "When I see something that I don't like, I'm going to speak out because you can do that here. And again, I feel there are too many things happening that are taking our rights away.

"I think athletes have a duty to speak out when there is something that's not right, when they feel that perhaps social issues are not being paid attention to. As a woman, as a lesbian, as a woman athlete, there is a whole bunch of barriers that I've had to jump over, and we shouldn't have to be jumping over them any more."