A female genital mutilation specialist who discovered that all the girls in a group of 30 newly arrived immigrants to Sweden had been cut has called for compulsory gynaecological checks for all children in the country.

Anissa Mohammed Hassan, the Somali woman who co-led a pilot FGM session with the young women in the heavily immigrant district of Norrköping, called for the introduction of genital examinations for all girls in Sweden aged six, just as all boys have their testicles checked.

"The problem we have in Sweden is that there are no checks," she said. "Going to your local doctor's surgery is optional and visiting a school nurse is also optional."

The pilot in Norrköping, which grabbed headlines when it was wrongly reported that an entire school class of girls had been subjected to FGM, 28 in the most severe fashion, has trialled a new hardline policy in which school nurses are trained to routinely question young girls about whether they have been circumcised whenever they come in for treatment or a checkup, bypassing their parents.

Hassan called for the policy to be rolled out across Sweden. "We want all communities in Sweden to do what Norrköping does, with all school nurses routinely asking girls if they have been mutilated."

"If they have been cut, we then directly send them to social services, where we ask them when they were operated on, and whether they have smaller sisters."

She said the girls in the group briefed in April had been surprised that their health problems could be treated.

"They thought that their problems – how they can't pee, how they're in pain – were shared by all the girls in the whole world. But when I said that in Sweden you can get help for this, many girls came to the school doctor, saying 'please can you help me', and one after another they asked for help themselves, and that was fantastic."

But the manner in which the original story was portrayed has caused tension in Sweden. When Norrköpings Tidningar reported that every single girl in a school class of 30 had turned out to be circumcised – with 28 of them having their clitorises and labia cut away and their vaginas sewn almost shut – it was picked up by the media across the world, including by UK broadsheets.

Petra Blom Andersson, the local education department health official who gave the numbers to Norrköpings Tidningar, would not be interviewed, while Juno Blom, head of the local region's FGM programme, refused to comment on where the number came from.

"I don't want to talk about that for a lot of different reasons," she said. "Does it matter for the girls who are abused if they are in the same class or not?"

In fact the girls, aged 13-18, were part of a group of newly arrived immigrants from FGM high-risk countries brought together for an educational session as part of a new pilot project being launched in Norrköping. They had all been circumcised in their home countries.

Sara Johnsdotter, an anthropologist at Malmö University specialising in female genital mutilation, said the headline grabbing figure was not surprising. "I've worked in this field for the past 15 years and every few years there is a new drive from the government to end it, and there is an accompanying report in a newspaper to give it more attention," she said.

"Personally, I think it is dangerous. It is harmful to the girls and women affected. It is the wrong kind of attention and it's stigmatising them further."

She sees the way the Swedish media reported the story as symptomatic of "a frustration about immigration in a multicultural society".

"We have to be so tolerant all the time," she said. "But [when it comes to FGM] you can say what you want and still be morally superior."

At the Somali cultural centre in Hageby, a heavily immigrant district of Norrköping, one Somali woman took offence at how the story had been told.

"It's not true that girls can't pee," said Nora Dore, whose son Abdinasir runs the centre. "The whole time you are talking about the clitoris being thrown away. Why are you doing it? You are talking about cutting, cutting, cutting, the whole time. It's a Muslim woman's problem, it's not your problem."

She said all Somalis living in Sweden now understood that FGM was a negative practice. "In Somalia, here, everywhere they are stopping it. The Qur'an says 'don't do it'. The whole time on the Somali channels nowadays they say you have to stop it."

She said she herself was circumcised and had ensured that her now 25-year-old daughter was before they moved to Sweden in 1994.

"We used to think that it was better, and the children, they wanted to do it," she said. "We thought that those who aren't cut would chase after men before they were married, and that they would have a baby without a father."

Other women at the centre supported the county government's decision to introduce automatic questions about FGM for girls from practising countries. "That's very important," said Amina Mire, 41, whose eight-year-old and 16-year-old daughters are not circumcised. "As long as there are people who are ignorant, you can only discover it during a health check."

But even if it is suspected that girls are cut while resident in Sweden, either while visiting their country of birth or in their adopted country, it it difficult to prosecute, Anna Nedvik, a detective in the local police, explained. She has worked with Andersson to prosecute the parents of one local schoolgirl, but the case never made it to court.

"We couldn't prove that it [the circumcision] had happened while there was a connection with Sweden," she said. "If you've done it while you're in another country, there must be some kind of connection with Sweden when it was done."

Sweden was the first country in the world to ban FGM in 1982, and in 1999 the ban was extended to include circumcision carried out in other countries. But police have struggled to apply the law, securing only two convictions in more then 30 years.

But, as the pilot demonstrates, the days when health, police and social services may have been reluctant to tackle FGM because of cultural sensitivities are over, said Johnsdotter. "That is not the case in Sweden, people in fact say the opposite that it is racist not to protect African children from abuse, or think they do not merit the same protection."