A London doctor who refused to approve a kidney transplant of an alleged victim of organ trafficking said he was worried that the man was being “financially coerced” into the donation, the Old Bailey has heard.

Dr Peter Dupont, a kidney specialist at the Royal Free hospital, was giving evidence at the trial of a Nigerian senator, Ike Ekweremadu, 60, his wife Beatrice, 56, daughter Sonia, 25, and Dr Obinna Obeta, 51, who are accused of conspiring to arrange or facilitate the travel of the young man to Britain with a view to his exploitation.

In February last year, Dr Dupont assessed the 21-year-old man, who cannot be named, as a potential donor for Sonia, who suffers from a serious kidney problem, the court heard. He outlined a series of concerns he had about the man, as well as the claim he was Sonia’s cousin.

Dr Dupont said he established there was “wealth disparity” between Ekweremadu and the potential donor after hearing the young man’s parents were street traders in Lagos.

He said this “creates a risk, and the risk is financial coercion”. He told the court: “You worry that some reward, financial or otherwise, has been promised to the donor in return for them coming forward to donate. Even if they deny it.”

He added: “We’re clinicians, we’re not the FBI or the CIA. We have no means to investigate people. We have to go on our clinical instincts as potential red flags and risks in this situation.”

Asked by prosecutor Hugh Davies KC about the man’s suitability as a donor, Dr Davies replied “it was a straight no”.

Dr Dupont added: “He appeared to be younger than the 21 years that was presented. I wanted to explore what had motivated him to come forward. His answers were brief, single sentences, single words. He didn’t really appear to have any understanding about what it was he was signing up for.

“You want to hear they have an understanding and motivation to help the prospective recipient, that they’re likely to have a close relationship with a prospective recipient. I wasn’t really hearing that from this young man.”

Speaking through an Igbo translator and Royal Free staff member who was being paid by the Ekweremadus, the man told the doctor he had last met Sonia when he was eight years old, the court heard.

Dr Dupont said: “He said they hadn’t had much of a conversation since his offer to donate. And that struck me as being a little incongruous.”

He added: “I just worried about the nature of the relationships with the recipient. It seemed very distinct. They hadn’t seen each other in many years. They’re weren’t close contacts. They had barely spoken since.”

The Ekweremadus, who have an address in Willesden Green, north-west London, and Dr Obeta, from Southwark, south London, deny the charge against them.

The trial continues.