A motorcyclist has been rushed to Christchurch Hospital in a critical condition following a serious crash on the Christchurch Southern Motorway.

The single motorcycle crash occurred about 5.55am on the Halswell Junction Road off-ramp near Hornby.

A St John spokesperson told chrislynchmedia.com one ambulance and a rapid response unit attended the scene.

“Our crews assessed and treated one patient who was transported to Christchurch hospital in a critical condition.”

The off-ramp remains closed while the Serious Crash Unit examines the scene.

Motorists are being advised to use alternative routes while the investigation continues.