A mother who claimed asylum fearing that her daughters would be mutilated if they were sent back to Nigeria is due to be deported after being detained on Wednesday, her supporters have said.

Afusat Saliu, 31, and her two daughters, Basirat, three, and Rashidat, one, have been taken into custody by Home Office officials and transported from their home in Leeds to London for removal, the family's lawyer told the Guardian.

Saliu, 31, a victim of female genital mutilation, has said that she fears her daughters will also be mutilated and spoken of her fear that, as Christians, they could be targeted by the Nigerian Islamic extremist group Boko Haram, which recently kidnapped more than 200 schoolgirls.

A petition calling on the Home Office to reconsider her case has been signed by more than 120,000 people. Saliu's lawyer, Bhumika Parmar of BP Legal, said her client had applied for permission to bring a judicial review and she expected the deportation to be put on hold while that was considered. But Parmar said that Home Office officials did not even inform her that her client was being detained and refused to tell her where she was being taken on Wednesday.

She said she only found out that the family had been taken when one of Saliu's friends made contact. She finally found out Saliu was being driven to London late on Wednesday evening, when her client was already en route.

Parmar also accused the Home Office of failing to follow its own rules by not giving Saliu the minimum 72 hours' notice of removal. "Her treatment has been very unfair," she said. She added that it worried her to think what would have happened to Saliu had the friend not called in time. "The fact that the Home Office did not come back to me to tell me where she was meant that I could not file a bail application," she said.

In a letter to Home Office officials sent as she sought to find out her client's whereabouts on Wednesday afternoon, she said that Afusat and her daughters were being deported before their welfare and right to a fair hearing had been properly considered. She threatened the Home Office with a claim for damages if the removal was not delayed until due process could be observed.

She wrote: "You have clearly breached your own policy. Furthermore, you have not advised that our client will receive the relevant protection required in Lagos, especially in light of the public interest in her case. You have failed to consider that our client has no support if she is to be returned, especially with two very young children. What proposals are there to house and maintain the family unit once she arrives in Lagos?"

Anj Handa, a friend of Saliu who set up the petition on campaigning website Change.org, said: "We have asked, please do this properly. It is almost like they are hell-bent on getting rid of her because we got the campaign going. The political timing is bad because the Home Office wants to show it is tough on immigration."

She said she did not want to see her friend become a victim of "political posturing".

Nigeria is home to the highest number of women subjected to FGM in the world and Saliu said her family do not want to subject her daughters to it. In April, after winning a temporary reprieve with the help of her MP George Mudie, she said she would not allow it.

"I don't want them to be mutilated. I know it will happen if I have to go back with them, I know it because it is the culture of my family," she said.

She added: "They believe in it and I will not be able to do anything about it. Every woman should stand up for her children and do whatever is necessary to protect them from something like this."

She arrived in the UK in 2011, and says she fled Nigeria when her stepmother told her that her oldest daughter, Bassy, would be cut. Her youngest daughter was born in Britain.

The Home Office said it does not comment on specific cases.