Tourists and young couples ambling through the historic centre of Krakow on a warm spring afternoon were stopped in their tracks by a sight reminiscent of the era of martial law. As drinks flowed in the open-air cafes of Poland's ancient royal capital, a phalanx of armed police in full riot gear inched its way slowly through the medieval city.

But unlike the 1980s when authorities crushed dissent, today's black-clad police officers were protecting the right to free speech of hundreds of gay and lesbian marchers holding their annual parade in Krakow. The precautions were wise: within 30 minutes stone-throwing far-right skinheads stormed the protesters from a side street.

"Faggots", the skinheads screamed as they were beaten back by police charging with batons. "Tolerance", the gay and lesbian marchers shouted back, as the far right were joined by smartly dressed protesters from a deeply conservative Polish youth movement.

"Homosexuals are deviants," said 19-year-old Liliane Sobczak, a leader of the Mlodziez Wszechpolska group whose members travelled from across Poland to "protect the family".

The scenes in Krakow provided a telling illustration of a new dividing line between parts of eastern Europe and the western half of the continent. While gay people in western Europe are increasingly treated as equals in the eye of the law, those in much of the east face discrimination and intolerance.

Days after the violence in Krakow, egg-throwing skinheads and elderly Orthodox women disrupted a gay night at a Moscow nightclub. Gay clubbers, who endured homophobic taunts as they were evacuated from La Guardia club under police escort, complain of persistent discrimination in the Russian capital. Yuri Luzhkov, the populist mayor of Moscow, has become a focus of their anger after he pledged to ban the first gay rights march due to take place later this month "to protect the feelings of Muscovites".

This experience is shared in other parts of eastern Europe, though not on the same scale. Zsolt Semjen, the leader of Hungary's Christian Democratic People's party, declared in the recent election campaign: "We have had enough of the deviances." But Mr Semjen's attempt to court conservative voters backfired as the right lost the election. Latvia, another recent entrant to the EU, amended its constitution last year to ban gay marriages.

Gay rights groups are most concerned about the climate in Poland, particularly after the highly conservative League of Polish Families joined the coalition government last week. The league, whose youth group took part in the anti-gay march in Krakow, is even more socially conservative than the president, Lech Kaczynski, who banned gay marches as mayor of Warsaw, or Kazimierz Marcinkiewicz, the prime minister.

Mr Marcinkiewicz summed up the thinking in the coalition's main Law and Justice party when he told the Polish edition of Newsweek: "If [a] person tries to infect others with their homosexuality, the state must intervene in this violation of freedom."

The assumption that gay people want to spread a diseased lifestyle encourages Catholic groups who have long targeted homosexuality. Thousands of headteachers have received a 29-page booklet from the fundamentalist Piotr Skarga Catholic association, named after a 16th-century Polish Jesuit, which issues instructions on how to ensure youngsters do not become gay. Entitled Taboos about Homosexuality, the pamphlet uses graphic language to scare young people . "Around 75% of homosexuals admit they put their tongue into their partner's anus which means they eat lots of faeces," the booklet tells teachers. "Homosexuals crawling in faeces and eating it suffer bad health."

The booklet attempts to depict gay people as blood suckers. In a section on oral sex, it says: "Sperm has bacteria which is transferred from blood. So homosexuals almost drink blood."

To round off its attack, the booklet declares that homosexuals die young and end up as killers after "research" found that murderers are invariably gay when their sexual orientation is determined.

Such homophobia is alarming gay and lesbian Poles. "I like this country but this intolerance is very sad," said Anna Zawadzka, 33, who lost her job as a special needs teacher at a rural school outside Warsaw after appearing on television to discuss her life as a lesbian.

"A parent who saw me complained to the local priest. He went to the headteacher and said that the school cannot employ a lesbian. The school then refused to renew my contract even though they had recently written me a letter saying how good I was."

A law was introduced by the previous Polish government banning discrimination on the grounds of sexual orientation, but Ms Zawadzka does not believe this would have made any difference. She said she was not given a reason for her contract being terminated."Most of the intolerance is indirect," she said.

Her view is shared by Krystian Legierski, who lost a two-year battle to run a gay nightclub in Warsaw in March when police closed down the premises. The city authorities, who own the building, were careful not to object to the club on the grounds that it was used by gay people.

"The city, which was then led by Lech Kaczynski, just devised lots of administrative ways to close us down," said Mr Legierski, 28. "First they tried to stop us selling alcohol. Then they tried to claim we were not paying rent."

A lengthy legal process ended when police officers marched into Le Madame club to enforce a court order by removing supporters. Mr Legierski said the officers seemed to be embarrassed. "The police said: 'We're sorry but we have to do this,'" Mr Legierski said in his new club, which is based in a building outside the city's control.

In western Europe, same-sex couples can now register their partnerships in several countries including Britain. Even Catholic Spain has legalised gay marriage as part of a series of revolutionary changes by the Socialist government.

Christine Loudes of the European branch of the International Lesbian and Gay Association said there were divisions across Europe, though she believed it was simplistic to talk of a clear east-west split. The Czech Republic has recently legalised same-sex partnerships, while a minister in Silvio Berlusconi's outgoing Italian government described a recent gay rights parade as "really nauseating". "There is a division," Ms Loudes said. "But attitudes depend on whether a conservative or a progressive government is in power."

With the hard right at the heart of the Polish government, traditionalists will enjoy the upper hand for some time. Waving a red-and-white Polish flag at the Krakow march with fellow protesters from the Catholic Mlodziez Wszechpolska youth group, Krzysztof Bosak said: "Violence is bad but there is no way you can protest against this abnormality without violence."