Britain's BBC on Thursday accused the Iranian regime of perpetrating "unprecedented levels of intimidation" against families of its employees on the eve of the country's presidential vote, AFP reports.
The broadcaster said authorities had warned the families of 15 BBC Persian Service staff working in London that their lives were at risk.
"In the past few days alone 15 family members have been questioned by the Iranian intelligence ministry in Tehran and other cities across the country", Liliane Landor, head of languages services at the BBC World Service, said in a statement.
"The harassment has included threats that relatives will lose jobs and pensions and be prevented from travelling abroad.
"For the first time the lives of BBC Persian TV staff living in the UK have also been threatened," she added.
Some 50.5 million people are eligible to vote on Friday for a successor to hardline leader Mahmoud Ahmadinejad, under whose presidency Iran has been isolated internationally over its controversial nuclear drive.
Four years ago, reformist hopes of returning to power were dashed by Ahmadinejad's re-election, sparking protests that were crushed by the security forces.