Police are investigating the circumstances surrounding a serious motorcycle crash in the Newcastle area overnight which has left a man critically injured.

About 12.15am (Monday 26 January 2015), a 29-year-old man was riding a Honda CBR250R motorcycle along King Street at Warners Bay.

As the motorcycle passed the intersection with Myall Street it has struck a kerb, mounted the footpath and travelled some distance before striking a sign post.

The driver was thrown from the machine onto the roadway and was discovered by other motorists who contacted police.

Officers from Lake Macquarie Local Area Command attended along with Ambulance Paramedics who conveyed the rider to John Hunter Hospital in a critical condition.

Investigators believe that alcohol and speed may have been factors in the crash and that the man was not licensed to ride motorcycles.

Inquiries into the incident continue and police have urged anyone that might have witnessed the incident to come forward.