National Highways says traffic can only pass in lane one northbound.
A statement said: “Lanes 2, 3, and 4 (of 4) are closed on the M6 northbound between J14 and J15 due to a significant offal spillage. Traffic can still pass the scene of the incident in lane 1.
“Initial attempts to arrange specialist cleanup equipment at the scene were unsuccessful. Alternative arrangements have now been made with neighbouring regional teams to bring the necessary equipment to the site.
“The incident is causing severe delays of up to 90 minutes between J12 and J15 of the M6 with very heavy congestion for up to 7 miles.”