The first challenge to regulations which allow benefits to be cut off for failed asylum seekers with children has failed at the High Court.
The controversial regulations were introduced last year
A Congolese woman had argued that cutting off support breached the Children Act and Human Rights Act.
But the judge, Mr Justice Bean, said it was for Parliament, not the courts, to decide if the policy was desirable.
Asylum seekers without means to support their children risk having them taken into care.
The mother-of-three bringing the case, known only as 'K', came to the UK in 2002 but had her benefits stopped last August after losing her case for asylum.
Appearing for the mother, barrister Stephen Knafler said the policy was putting children at risk of trafficking, sexual exploitation, illegal working and other abuse.
But Elisabeth Laing, appearing for the home secretary, said the scheme was "legitimate" and was designed to ensure a breach of human rights should not take place.
Refusing K permission to seek a judicial review, Mr Justice Bean said he did not consider it was arguable that the policy was incompatible with the European Convention on Human Rights.
The failure of the test case comes as charities claim failed asylum seeker families facing loss of benefits are going into hiding.
A Home Office scheme piloting the new powers has been taking place in three areas - central and east London, Greater Manchester and West Yorkshire - and involved 116 families.
The Refugee Council and Refugee Action said 32 families have gone underground to avoid having their children taken into care if they fail to leave.
The Children's Society said it was aware of 35 families who had vanished rather than comply with removal orders.
When the trial of the new regulations began last January the Home Office said they were simply a method of persuading families who had exhausted their asylum appeals to leave voluntarily.
Ministers denied seeking to use the threat of children being taken into care as a way of enforcing removals.
A Home Office spokesman said: "The government is currently carrying out a pilot of the Section Nine policy and will undertake a detailed analysis.
"Section Nine only applies to failed asylum seeking families and is intended to act as an incentive to return voluntarily.
"It is not designed to make families destitute or split families up."