The 22-year-old came off the bike on waste land at Scotland Gate, in Choppington, at 1908 BST Saturday.

The man, from Bedlington, was not wearing a helmet, and was taken to Wansbeck General Hospital with serious head injuries.

He was later transferred to Newcastle General Hospital.

Northumbria Police said they would like to trace other riders who were seen in the area at the time, especially the rider of a quad bike.