LONDON (Thomson Reuters Foundation) - Nigeria is failing to enforce a much heralded ban on female genital mutilation, activists said on Friday, as they urged the country to sort out a “messy patchwork” of laws and beef up efforts to protect girls.

A quarter of women in the West African country have undergone the agonizing ritual, which can cause serious health problems.

Most girls who have the procedure are cut before the age of five, according to a report on Nigeria’s FGM laws by campaign group 28 Too Many.

Although Nigeria introduced a federal law banning the internationally condemned practice in 2015, it only automatically applies in the Federal Capital Territory of Abuja. Other states have to pass mirroring laws.

However, the study showed only 13 out of 36 states have outlawed FGM with penalties ranging from modest fines to five years’ imprisonment.

“It’s shocking to see that so many states still don’t have laws. This is something Nigeria needs to sort out if it’s serious about ending FGM,” said Ann-Marie Wilson, executive director of 28 Too Many.

Researchers said enforcement of the law was generally weak and found no evidence of any FGM prosecutions even though some states banned the practice more than 15 years ago.

The maximum penalty under the federal law is four years or a fine of 200,000 naira ($654).

Nigeria accounts for a tenth of the estimated 200 million girls and women globally affected by FGM, which usually involves the partial or total removal of the external genitalia.

Although the ancient ritual remains deeply entrenched in some southern regions, more than 60 percent of Nigerians say it should end, according to the study facilitated by TrustLaw, the Thomson Reuters Foundation’s legal pro bono service.

Researchers said Nigeria’s law failed to provide a clear definition of FGM, did not stop parents taking children to other countries to be cut and did not address a growing global trend for nurses and midwives to carry out FGM.

National data suggests about 12 percent of Nigerian girls undergoing FGM are cut by a medical professional rather than a traditional cutter.

Laws in other countries like Burkina Faso and Senegal stipulate that medical professionals who perform FGM should face the maximum penalty.

The report also highlights concerns that a clampdown could push parents to have their daughters cut in neighboring countries.

Unlike some other African countries, Nigeria has not criminalized cross-border FGM.

Researchers said inconsistencies in Nigeria’s state laws also created a risk that parents in a state which had outlawed FGM could take their daughters to a state which had not.

“We need to push for consistent laws and enforcement across the whole of Nigeria, otherwise people could get away with it simply by traveling to another state,” said Wilson.