British Transport Police (BTP) said the actions of Joshua Tilt, who was sacked after his resignation was refused, were "sickening and completely incompatible with both public decency" and what is expected of force staff.

He was arrested after telling a colleague he had sent the image to his girlfriend.

Birmingham Crown Court was told the 31-year-old used his personal mobile phone to photograph a "highly sensitive" picture of RAF cadet Lewis Williams, 18, which was displayed on a computer screen.

The youngster, described by his family as "popular, funny and kind", was diagnosed with emotionally unstable personality disorder before his death in Slough, Berkshire, in June.

His parents were in court for Friday's 15-minute hearing to see Tilt plead guilty to misconduct in public office.

Tilt, of Lye Close Lane, Bartley Green, Birmingham, was granted unconditional bail but told he is likely to face a custodial sentence.

In a statement, BTP said Tilt took a picture on his mobile phone on 21 June of an image from the scene of a railway fatality.

The force added: "On 30 June Tilt was arrested and interviewed, where he admitted sending the same image on WhatsApp to a group chat with 12 people in.

"Tilt tried to resign but the force rejected his resignation and dismissed him formally without notice two weeks later on 14 July."

The force's deputy chief constable, Alistair Sutherland, said: "As an organisation, we take great pride in supporting families through some of the darkest days of their lives, and treating each of them with care, compassion and respect.

"To know that the actions of one of our employees actually intensified the suffering of a family is something that we find incredibly distressing.

"Our chief constable visited the family to explain what had happened and apologise unreservedly."

Lewis's father, Paul, has previously told how the family were informed on 2 July that BTP had launched an investigation into a member of staff.

Mr Williams, from Slough, said he was told someone had "gained access to the police aftermath scene photos, chosen a photo of his (Lewis's) dismembered body and then shared the image in a WhatsApp chat group with 14 others".

"I immediately felt sick," he said.

Adjourning sentence on Tilt, Judge Paul Farrer KC told him: "You have pleaded guilty to what on any view is a serious offence involving gross misconduct in the course of your employment.

"You have heard me indicate to your counsel that the likely sentence is one of imprisonment."

Tilt, who left court without comment, will be sentenced on 14 December.