How much can we risk the safety of a small child? What if that risk was of female genital mutilation? And what if the child was born in Britain but is being sent to a country where FGM is prevalent?

Surely the government should be concerned. Just weeks ago education secretary Michael Gove, urged on by the Guardian's anti-FGM campaign, agreed to write to headteachers reminding them of their duty to protect schoolchildren from cutting. And in February it was revealed that parents suspected of taking their daughters to Africa for FGM are to be stopped by police at airports.

But instead of concern, the government is actually forcing this child, against the wishes of her mother, to leave Britain and be sent to Nigeria. The child in question is Rashidat, now two, who was born in the UK after her heavily pregnant mother, Afusat Saliu, fled Nigeria to escape a forced marriage to a much older man – and to evade the imminent threat of FGM on her other daughter, Bassy, now four.

Afusat's fear that her daughters will be pinned down and mutilated if they return to her village is real. That is what happened to Afusat herself as a child.

I have met Afusat and her lovely daughters. I've helped support their pleas to stay safe in Leeds, where they came to live. Her friend Anj Handa has led a last-ditch e-petition to home secretary Theresa May against Afusat's deportation, now signed by 100,000 people. "Her children are at high risk of FGM," says Handa. "She has no support in Nigeria, no family protecting her from FGM that she can turn to; she's terrified of going back." Handa says Afusat has consistently complied with immigration rules – and will continue to engage with the immigration service. Her desperate hope is that George Mudie, Afusat's MP in Leeds East, will be able to secure a last-minute review.

Mudie is urging Home Office minister James Brokenshire to delay the deportation, but supporters cannot confirm whether or not she will fly today. Nigeria has the highest absolute number of FGM cases anywhere in the world. About a third of women in the country have undergone FGM. Some who undergo FGM die; most suffer permanent damage. FGM in Nigeria is officially illegal, but kidnappings by traditionalists are a feature of its enforcement.

The United Nations and the EU recognise the risk of FGM as grounds for asylum, but the UK Border Agency under May's control, apparently know better.

The hypocrisy is startling. The UK coalition government declares itself determined to lead the eradication of FGM globally within a generation. Britain should be applauding women like Afusat, often having been harmed themselves, who have had the courage to defy the devastation of FGM.

The UN special envoy, Prof Rashida Manjoo, recently shared her concerns about refugee, trafficked and asylum-seeking women who face "insecure immigration status" in the UK. Sadly, Britain seems determined to demonstrate human-rights-denying callousness in the way it deals with women and children vulnerable to FGM – even ones born in this country.

Even one woman or child who has FGM forced on her because she is deported from the UK is too many. It is surely unthinkable for that to happen to anyone.

So here's my challenge to May: prove to us that no one thus far deported has experienced FGM or other harmful traditional practices since they left our shores. Demonstrate that you have secured assurances from authorities in the relevant countries that they will keep deportees safe. Demonstrate that you are not a hypocrite.

And don't deport Afusat and her little girls unless you can be 100% certain that this safety net is in place in Nigeria, right now.

I would like to be proud of my country's record on human rights. At the moment I am deeply ashamed. It can never be OK to send small children away to risk atrocities like FGM.

• The epetition can be signed here