Drivers on the southbound motorway faced delays of an hour after the crash happened near Junction 7 at Great Barr shortly before 10am on Tuesday. The carriageway was shut between Junctions 7 and 6 with roads throughout the Black Country congested as a result.
Ambulance workers attended and one man was treated for minor injuries before being taken to hospital, but drivers who blocked the closed lanes and delayed the ambulances were criticised.
A statement from the Central Motorways Police Group said: "Thanks for the patience of people stuck in the closure earlier M6 Junction 7 to Junction 6. There was a five-vehicle [collision] involving four HGVs.
"To those motorists who couldn’t be bothered to wait and end up blocking the closed red X lanes, you delayed the ambulance and medical treatment.
"As the ambulance was stuck due to vehicles blocking the closed lanes we had to get another ambulance to travel the wrong way from Junction 6, which resulted in the traffic being held for a lot longer.
"Please, please obey the red X's, they are there for a reason."
Jordan Eggington on behalf of West Midlands Ambulance Service said: "We were called at 9.43am to reports of a collision involving multiple HGVs between Junctions 7 and 6 of the M6. We sent one ambulance and a paramedic officer to the scene.
"We’ve treated one patient, a man, for minor injuries, and he was conveyed to Queen Elizabeth Hospital in Birmingham for further treatment.”
The lanes were reopened and traffic moving again by about 12.30pm.