Britain's richest doctor has threatened to sue Panorama after what he claimed were defamatory allegations about techniques used at his fertility clinics.
Mohamed Taranissi, a leading IVF expert, claimed the programme has caused lasting damage to his professional reputation.
Carter-Ruck, the libel lawyers, wrote to the BBC on behalf of Taranissi, signalling his intention to sue on a complaint of defamation. The BBC has 14 days to respond.
The investigation into Taranissi, broadcast in January, claimed that one of his central London clinics, the Assisted Reproduction and Gynaecology Centre (ARGC), offered "unnecessary and unproven" treatment to an undercover reporter posing as a patient.
The programme claimed he also was running a second clinic, the Reproductive Genetics Institute (RGI), without a licence and was sending his older and harder-to-treat patients there to maintain a high success rate at the ARGC.
The BBC said it would reply "in due course" to the letter.