"Their advertisements offering kidney have appeared on the internet and five of them corresponded with undercover journalists, who posed as friends and relatives of sick patients to negotiate sales," The Sunday Times claimed.
One person willing to sell a kidney is a 26-year-old mental health nurse who said he wanted the money to pay debts after his business collapsed, the report said.
Another, a 43-year-old taxi driver from Lancashire, sought to raise the cash to pay off some of his mortgage and buy a new kitchen.
Meanwhile, a doctor said the phenomenon highlighted the need for a public debate on the issue of selling organs.
The report also said, about 7,000 people in the UK are waiting for kidney transplants and 300 died last year while on the waiting list.