Conditions in Texas migrant detention centres are the “worst I’ve ever seen”, a Republican from the state has admitted, after reports from lawyers suggested children were enduring lice infestations, flu infections and nights sleeping on cold concrete floors.

Representative Michael McCaul added that “at a minimum”, Congress should create a humanitarian aid package for young people being held near the US-Mexico border. He blamed a lack of action by politicians for the filthy conditions.

Speaking on CBS’s Face The Nation programme, he said: “I’ve been down there throughout my 15 years in Congress and before that, as a federal prosecutor. This is the worst I’ve ever seen it, and it has to be taken care of.”

He would vote for a “compassionate, humanitarian package” whether or not it was tied to wider border security measures, he said.

It came after a lawyer working with migrant children detained at Border Patrol facilities in Texas raised concerns for their welfare.

Warren Binford said she had met children who had been held for weeks at a time – when the limit is 72 hours – with hundreds living together in a windowless warehouse at one base in Clint, in El Paso county.

Families were separated and older children made to care for younger ones, she told the New Yorker magazine. “The United States is taking children away from their family unit and reclassifying them as unaccompanied children.

“But they were not unaccompanied children. And some of them were separated from their parents.”

She added: “We received reports from children of a lice outbreak in one of the cells where there were about twenty-five children, and what they told us is that six of the children were found to have lice.

“They were given a lice shampoo, and the other children were given two combs and told to share those two combs ... which is something you never do with a lice outbreak.

“One of the combs was lost, and Border Patrol agents got so mad that they took away the children’s blankets and mats. They weren’t allowed to sleep on the beds, and they had to sleep on the floor ... as punishment.”

Some children had not been able to shower or brush their teeth for some days, Ms Binford told the magazine, while some had caught flu.

At the weekend, Mr Trump delayed a planned migration crackdown in 10 major cities “at the request of Democrats”, in order to give politicians a chance to resolve the border issue that has plagued his presidency.