Theresa May has condemned the forced separation of migrant children from their parents at the US-Mexico border, but dismissed calls to cancel President Donald Trump's visit to the UK.
The PM said the images of children being kept in what look like cages was "deeply disturbing" and "wrong".
But she said Mr Trump's visit next month should go ahead to ensure "shared interests" could be discussed.
Where she disagreed on something, she would tell Mr Trump, Mrs May insisted.
She was challenged on the issue at Prime Minister's Questions by the SNP's Ian Blackford and a host of Labour MPs, including former leader Ed Miliband.
Mrs May said she was "clearly, wholly and unequivocally" clear that she disagreed with the policy.
"On what we have seen in the United States, pictures of children being held in what appear to be cages are deeply disturbing," she said.
"This is not something that we agree with, this is not the United Kingdom's approach."
But she said the UK had a "long and enduring special relationship" with the US and Mr Trump's visit next month was an opportunity to raise a range of issues.
The Republican-controlled Congress is under pressure to change the border policy, following widespread condemnation. But the president says it is necessary to stop illegal border crossings.
The "zero-tolerance" policy - brought in by US Attorney General Jeff Sessions last month - means that adults who try to cross the border, many planning to seek asylum, are placed in custody and face criminal prosecution for illegal entry.
As a result, hundreds of minors are now being housed in detention centres, and kept away from their parents.
On Tuesday, Mr Trump said children had to be taken away if their parents were jailed for illegally crossing the US border.
"When you prosecute the parents for coming in illegally - which should happen - you have to take the children away," he said.
US immigration officials say 2,342 children were separated from 2,206 parents between 5 May and 9 June.
Babies and toddlers have been sent to three "tender age" shelters after being separated from their parents, the Associated Press news agency reported.
Doctors and lawyers who visited the shelters described the infants as hysterical, crying, and acting out, according to the AP report.
Mr Trump is due to visit the UK on Friday, 13 July.