The Dover area school board violated the constitution when it ordered that its biology curriculum must include intelligent design (ID), district judge John Jones said.

The policy, adopted in October 2004, is believed to have been the first of its kind in the country.

"The citizens of the Dover area were poorly served by the members of the board who voted for the ID policy," Judge Jones wrote in his 139-page judgement.

"It is ironic that several of these individuals, who so staunchly and proudly touted their religious convictions in public, would time and again lie to cover their tracks and disguise the real purpose behind the ID Policy.

"We find that the secular purposes claimed by the board amount to a pretext for the board's real purpose, which was to promote religion in the public school classroom."

The board's attorneys said members sought to improve science education by exposing students to alternatives to Charles Darwin's theory of natural selection, or evolution. Intelligent-design supporters argue that it cannot fully explain the existence of complex life forms.

The district was sued by a group of 11 parents who claimed the intelligent design policy was unconstitutional and unscientific and had no place in science classrooms. They argued that intelligent design amounts to a secular repackaging of creationism, which the courts have already ruled cannot be taught in public schools.

The Dover policy required students to hear a statement about intelligent design before ninth-grade biology lessons on evolution. The statement said Charles Darwin's theory is "not a fact", has inexplicable "gaps", and refers students to ID textbook Of Pandas and People for more information.

Mr Jones said advocates of intelligent design "have bona fide and deeply held beliefs which drive their scholarly endeavours" and that he didn't believe the concept shouldn't be studied and discussed.

"Our conclusion today is that it is unconstitutional to teach ID as an alternative to evolution in a public school science classroom," he wrote.

The dispute is the latest chapter in a long-running debate over the teaching of evolution dating back to the famous 1925 Scopes monkey trial, in which Tennessee biology teacher John Scopes was fined $100 (£57) for violating a state law that forbade teaching evolution. The Tennessee supreme court reversed his conviction on the narrow ground that only a jury trial could impose a fine exceeding $50, and the law was repealed in 1967.