Cast member Liam Neeson arrives for the premiere of the film ''The Next Three Days'' in New York
Liam Neeson's nephew was enjoying a night out with friends when the accident happened.Reuters

The nephew of actor Liam Neeson is in a critical condition after suffering a serious head injury on a night out.

Ronan Sexton, suffered serious head injuries after falling 20ft from a telephone box near Brighton Pier, East Sussex, on Sunday (22 June).

Mr Sexton had been enjoying a night out with friends when the accident happened after he climbed onto the phone box and fell.

He was admitted to a local hospital but then transferred to Hurstwood Park neurological centre in Haywards Heath, West Sussex, in a critical condition.

Sussex Police said there were no suspicious circumstances surrounding the incident.

A police spokesman said: "Just after 4am on Sunday, June 22, a 30-year-old Worthing man had climbed on to the top of a telephone kiosk outside Brighton Pier when he fell 20ft to the ground, sustaining a serious head injury.

"He was taken to the Royal Sussex County Hospital and was later transferred to Hurstwood Park Hospital in Haywards Heath where he is currently in a critical condition.

"The man had been enjoying a night out with friends, who were present when he fell, and the incident is not being treated as suspicious.

"There is no further police investigation."

The 30-year-old is the son of the Love Actually actor's sister Bernadette Sexton.

Ms Sexton is said to be at her son's bedside where he is fighting for his life.

It's the latest tragedy to befall the family. Five years ago, Neeson's wife Natasha Richardson died after hitting her head while skiing in Canada. She was 45.

In an interview with US show 60 Minutes in February, the Irishman said he was still struggling to come to terms with her loss.

He said: "It was never real. It still kind of isn't. There's periods now in our New York residence when I hear the door opening - she would always drop the keys on the table and say hello.

"So any time I hear that door opening I still think I'm going to hear her. Grief hits you like a wave, you get this profound feeling of instability."

The Taken star, 62, now lives in New York with their two teenage sons.