Local councils are unlawfully denying destitute children support because their parents’ immigration status is under suspicion, the Guardian can reveal.

Families whose immigration status becomes insecure can quickly become destitute because they lose their right to work and access benefits. Such families who have dependent children can seek support under section 17 of the 1989 Children Act, which states that local councils have a duty to provide cash or accommodation to ensure a child’s immediate needs are met.

Hundreds of these families have been unlawfully denied this support since 2010 because local authorities have focused on the parents’ immigration background.

Many of the children affected are either British or entitled to British citizenship, and campaigners say it has now become normal practice for them to threaten local authorities with legal action in an effort to ensure a fair assessment.

Rupinder Parhar, a policy officer at the Children’s Society said: “For families struggling with the ‘no recourse to public funds’ (NRPF) condition, local authorities can support but often refuse an initial assessment in spite of this contradicting the law. We usually have to resort to legal action where a local authority does not provide an assessment of a family’s needs.”

Eve Dickson, a policy officer at Project 17, which supports families trying to access section 17, said: “We find many local authorities are excessively concerned with trying to ‘catch parents out’. Any inconsistency in the information provided will be used to discredit them and refuse support. Children in these families are being failed because of this pervasive and discriminatory culture of suspicion.”

Ellen Tansey, the senior housing link worker at Solace Women’s Aid, said victims of domestic violence are among those who have been unlawfully denied support. “These children are being let down because of their mother’s immigration status. There’s a concern that had the parent been British at least an assessment would have been explored, whereas when they’re not, the door is often shut,” she said.

Rebecca, a mother in her early 30s who preferred not to give her last name, said she had been made to feel like a criminal last summer, when she sought section 17 support from Croydon council for her six-year-old British daughter. She said she was denied support for several months despite being homeless, and that the council only stepped in when a lawyer threatened legal action. “After all the pain, they finally agreed to help, but it was a struggle. I don’t want anyone to go through what I went through. It was too much. My child was left hating life,” she said.

In another case, a mother of three was forced to sleep in a bus shelter with her three children after Sandwell council refused her application for section 17 support. Mary, 35, who preferred not to give her real name, said she was consistently refused support for five months and told her family had no right to reside in the UK. “They started accusing me in front of my kids that I am lying about who I am and my situation. They said I should go back to my country with my kids. They said my children are illegal immigrants and don’t belong here,” she said.

Mary’s lawyer obtained a court order obliging the local authority to house her family, which it ignored until threatened with criminal prosecution. With the help of ASIRT, an organisation that supports asylum seekers and undocumented migrants in the West Midlands, Mary was eventually granted section 17 support, but she said the experience had left her traumatised.

Dave Stamp, a senior caseworker at ASIRT, said children, and frequently British children, have become casualties of the “hostile environment” put in place during Theresa May’s tenure as home secretary. “Essentially, we have come to anticipate that children will be left destitute without the prospect of legal action,” he said.

Jane Williams, the founder of the Magpie Project, which supports destitute families in the east London borough Newham, said: “Families are being left to fend for themselves. We’ve had children who have been turned out onto the street with their parents on a Friday night and told to come back on a Monday morning, even though they have nowhere to go. It’s absolutely terrifying that there are children in this country who are being ignored and kept destitute.”

The Labour MP Kate Osamor said: “It is unconscionable that children in the UK today are going without enough to eat and a safe place to sleep. Much of this is down to governmental departments’ incompetence, but a lot is down to local authorities deliberately putting up barriers to families seeking section 17 support.”

A spokesperson for Croydon council said: “Our duty of care to a child in need – section 17 of the Children’s Act - always comes first, regardless of their family’s immigration status. When a family with no recourse to public funds is referred to us for support, we will carry out an initial assessment to determine their circumstances and if it is clear that an immediate offer of assistance is necessary, for example, subsistence or shelter, we will provide this on a ‘without prejudice’ basis, pending the conclusion of a section 17 assessment.”

A spokesperson for Sandwell council said: “We take our responsibilities to protect vulnerable children and families very seriously and are completely satisfied the appropriate support was provided in Sandwell.” In Mary’s case, the council provided an assessment, temporary accommodation and weekly subsistence payment, they said.

• This article was amended on 27 May 2019 to clarify that the name of the 1989 act was the Children Act, not Children’s Act.