A News International spokesperson said:

Following allegations made yesterday by Gordon Brown against The Sun, we have been conducting an inquiry. This is in line with normal practice and procedure.

We are able to assure the Brown family that we did not access the medical records of their son, nor did we commission anyone to do so.

The story The Sun ran about their son originated from a member of the public whose family has also experienced cystic fibrosis. He came to The Sun with this information voluntarily because he wanted to highlight the cause of those afflicted by the disease. The individual has provided a written affidavit this afternoon to a lawyer confirming this.

On receipt of the information, The Sun approached Mr Brown and discussed with his colleagues how best to present it. Those colleagues provided quotes which were used in the published piece which indicated his consent to it. We believe that the article was written sensitively and appropriately. We are not aware of Mr Brown, nor any of his colleagues to whom we spoke, making any complaint about it at the time.

The publication of the story and the further responsible, sympathetic and informative coverage The Sun continued to give to the disease resulted in renewed interest for those affected by it. Donations to the Cystic Fibrosis Trust nearly doubled over the next year.

We continue to inquire in to other allegations made by Mr Brown, and implore him to provide details to us so we can establish the facts.