The son of a retired British businessman extradited to the United States over arms dealing charges has urged David Cameron to intervene to secure his father bail.
Neil Tappin, whose 65-year-old father Christopher is being held alone in a cell for 23 hours a day in New Mexico while he awaits trial, said his family was left "stunned" when a US judge refused bail earlier this month.
Mr Tappin spoke out in defence of his father as Mr Cameron visited the US for three days of talks with President Barack Obama.
He said his father "deserves the presumption of innocence before trial" and any officials who fail to recognise "that most basic principle should be ashamed".
"Our family asks for nothing more than the support of the UK Government in securing bail now my father is in the US," he said.
"The irony is that a British citizen is being accused of being a 'flight risk' by the US in part because he did nothing more than exercise his lawful right to resist extradition in the UK."
Mr Tappin added his father had always complied with his bail conditions in the UK and there was "no reason at all to conclude he is either a flight risk or a danger to anyone".
But Judge Robert Castaneda ruled on March 5 that Tappin must remain in custody after US prosecutors told the federal court in El Paso, Texas, he may be a "danger to the community" if released.
He agreed that measures could be imposed to ensure Tappin was monitored if released, but said a discrepancy in Tappin's financial statement led to him being denied bail.
Neil Tappin also hit out at "misinformation" surrounding his father's case.
"My father intends to demonstrate the fallacy of the prosecution's case at trial," he said.
Tappin faces up to 35 years in jail if convicted of attempting to sell batteries for surface-to-air missiles which were to be shipped from the US to Tehran via the Netherlands. He denies the charges.
He is being held at the Otero County detention centre in New Mexico and the date for his trial over the border in El Paso, Texas, has not yet been set.
Tappin has since been moved to a shared cell with four others, a family spokeswoman said.