A Muslim family of nine from London, including four children, have been refused permission to board a flight to the US out of Gatwick.
Mohammed Zahid Mahmood, from Walthamstow, eight members of his family and two other children checked in on Tuesday for the Norwegian Airlines flight to Los Angeles.
They had obtained travel authorisation under the Visa Waiver programme.
The family say they were told an official in the US had objected.
At the boarding gate Mr Mahmood said they were told they could not travel but no reason was given.
He said in order to use the VWP, the family's application to travel had been authorised by the Department for Homeland Security a month prior to the flight.
Detained in Tel Aviv
'"We checked in, there were no problems," Mr Mahmood told the BBC. "Just before the final check we were singled out.
"Border control came and said 'Can we have your passports?'. He asked us to distinguish between my brother's children and my children.
"Then he came back and said, 'I'm sorry you can't board this flight. We received a call from Washington DC that we can't allow this family to board the flight'."
Mr Mahmood said he had educated his children "to live in this country peacefully" and had been invited to speak at local schools about Islamophobia.
He said he had once been denied entry to Israel, and was detained at Tel Aviv airport for two days before returning to the UK.
"No-one is taking the blame. We are just going round in circles. It's about £8,000-£9,000 we've spent on tickets."
A spokesperson for Norwegian Airlines said: "We can confirm that a group of passengers were denied the right to board a flight from London Gatwick to Los Angeles yesterday at the request of US Homeland security. Norwegian fully complies with requests from the border controls of each country we serve."
The US Embassy could not be reached for comment and Gatwick Airport said they had no information about the incident.
Correction 23 December 2015: This story has been amended to clarify the amount of time Mr Mahmood says he was detained in Israel.