Firefighters and council crews are working to clean up a major diesel spill stretching over several Lake Macquarie suburbs.

Newcastle Fire Command says they were alerted to the spill at about 6.30 this morning, which stretches through Barnsley, West Wallsend, and Holmesville for 6kms.

Fire crews are on scene at Northville Drive at Barnsley and Withers Street at Holmesville where large pools of the fuel have been found.

The source of the diesel leak is understood to be a bus.

Council crews are using sand and a street sweeper to  clean up the rest of the spill.