The battle appears to be frivolous, involving, as it does, learned arguments over whether a navel is indecent, or a penis gourd, which guards the modesty of the Papuan male, constitutes nudity.

However, it is serious for dozens of people who have fallen victim to zealous prosecutors, police harassment and mob violence in a battle for the destiny of the world’s most populous Islamic nation.

The contest for the hearts and minds of more than 200m Indonesians is being closely watched by western nations, one reason for Tony Blair’s 24-hour stop here last week.

Blair saluted President Susilo Bambang Yudhoyono, a reformer with a reputation for honesty; held brief talks with moderate Muslim leaders; and fielded questions on Iraq, Palestine and George W Bush from an articulate group of boys and girls at one of Jakarta’s religious boarding schools.

But many Indonesians fear their president is losing his grip on a political debate increasingly dominated by fundamentalists, who have made a parliamentary bill on indecency the centrepiece of their campaign to purify the nation.

“This is an attempt by some people to import Arab culture to Indonesia,” said Yenny Wahid, a Muslim campaigner for women’s rights.

The draft bill would extend a ban on indecency to prohibit kissing in public, which would be punishable by five years in prison. Public nudity or the “indecent” exposure of the stomach, thigh or hip — some religious jurists argue that shoulders could also be deemed inflammatory — could be punished by a 10-year sentence and a £30,000 fine.

Although public displays of affection, let alone nudity, are rare in Indonesia, as in most Asian cultures, the authors of the bill have also sought to censure the wearing of tight or suggestive clothing.

Opponents of the draft are trying to strike out the more draconian clauses in parliamentary committees before the bill goes to a vote, which is expected in June. A delegation from Bali, a mainly Hindu island that makes its living from sun-seeking beach lovers, has hastened to Jakarta to state its opposition to the bill.

Politicians from Papua, which is racked by internal strife, have pleaded against any law that would insult tribal culture by forcing its indigenous folk to cover themselves in deference to the mores of 7th-century Arabia.

But political analysts in Jakarta have traced a series of incidents that show some local governments and religious tribunals are imposing their own version of sharia (Islamic law) through a stream of fatwas, or decrees, backed by police action.

In East Java, a former boxer turned preacher, Yusman Roy, 51, is in prison for “spreading hatred”. His offence: reading prayers in the local language, Bahasa Indonesia, instead of classical Arabic.

A religious high school teacher, Sumardi Tappaya, 60, is facing imprisonment after a complainant heard him “whistling” while performing prayers. Ardhi Husain, 50, who ran a prayer centre that employed faith to help the sick, has been sent to prison for five years for writing a book deemed “deviant” by the ever more vigilant Indonesian Council of Ulemas.

Its “deviance” lay in affirming, among other questionable doctrines, that non-Muslims could also enter paradise. The printer and publisher also received jail terms. But nobody was arrested after an irate crowd burnt down the prayer centre.

Such petty malice and mob violence are prompting fears of a harshly repressive moral climate for artists and intellectuals. Agus Suwage, an artist, is virtually in hiding after a furious crowd, offended by his painting of a nearly nude couple in an imaginary garden of Eden, forced the closure of the Jakarta Biennale arts festival. He, too, could face a jail term.

The fundamentalists say they want to curb Indonesia’s enormous sex industry and to protect its youth against bad influences such as the arrival soon of a local version of Playboy magazine — which will not, of course, contain nudes.

Defenders of the secular state point out that Islam arrived peacefully through trade, not conquest, in these islands to evolve into a tolerant, tropical version of the faith.

That is why Blair’s visit to a moderate Islamic boarding school last Thursday was so important.

Yet the risks in associating Indonesian moderation with the West were shown up by a boy of 16, Ardani Yusuf, who put Blair on the spot with a polite question about how he would feel if he was an Iraqi civilian who lost his family.

Blair replied with generalities. “He was cool,” said Yusuf, the next day, “but I asked him a personal question and he gave me a political answer.” Yusuf says he wants to become a psychologist.

Explore World News

• Iraq News

• US & Americas News

• Europe News

• Middle East News

• Asia News

• Africa News

• Ireland News

Times Recommends

• Afghanistan: A country locked in a spiral of doom
• Liberal challenges prohibitionist Islam
• Flying yacht in battle to crack 50-knot barrier