The Kansas board of education has narrowly voted to change the state's curriculum to question the validity of evolution, recommending that schools explore the "considerable scientific and public controversy" over the origins of life.

The 6-4 vote makes Kansas the fifth state in the country (after Ohio, Minnesota, New Mexico and Pennsylvania) to adopt a curriculum that challenges Darwinism in favour of what supporters call "intelligent design", a revised version of creationism which argues that living things are too complex to have evolved solely by random mutation and natural selection.

The state education board went further, changing the definition of science, expanding it to include supernatural explanations of natural phenomena.

Both the National Academy of Sciences and the National Science Teachers Association, whose material the state relies on, warned the board that they would revoke copyright privileges if the new curriculum was invoked.

Supporters of "intelligent design" claim that the move will allow children to hear all sides of the evolution debate. "This absolutely raises science standards," the Kansas board of education's president, Steve Abrams, told the Los Angeles Times. "We are brave enough to have all areas discussed," said a board member, Kathy Martin, who backed the change. "Students will be informed and not indoctrinated."

But critics say it merely introduces religion into education through the back door. "We're becoming a laughing stock, not only of the nation, but of the world," said one board member, Janet Waugh. "Why not be honest and say it is a faith issue? I personally believe in the biblical version of creationism, but I don't believe that my beliefs should be taught in a science class."

"This action is likely to be the playbook for creationism for the next several years," Eugenie Scott, director of the National Centre for Science Education told the Associated Press news agency. "We can predict this fight happening elsewhere."

On the other side of the country, meanwhile, intelligent design suffered a significant setback. Residents in Dover, Pennsylvania, voted out all eight members of the school board who had made local teachers read out a statement in biology classes casting doubt on the theory of evolution and encouraging them to explore intelligent design. They were replaced by candidates who opposed the statement.

The Dover statement has been the subject of a high-profile trial which pitted supporters of intelligent design against scientists who said its teaching violated the constitutional separation between church and state. Arguments concluded last Friday and the judge is expected to declare a verdict by the new year.

Two of the school board members who lost their seats this week had testified in court in support of intelligent design.

"I think voters were tired of the trial, they were tired of intelligent design, they were tired of everything that this school board brought about," Bernadette Reinking, one of the Democrat winners, told the New York Times.

Judy McIlvaine, who was also on the winning slate, added: "We were all for it being discussed, but we do not want to see it in biology class."

This is not the first time that Kansas state has been at the centre of the battle over evolution. Six years ago, its education board removed evolution from its curriculum, along with the big-bang theory of the creation of the universe. However, the decision was reversed in 2000, when Kansas voters ousted the most conservative members of the state board.