Speaking outside court, Mr Counsell said he believed the decision to prosecute him was "motivated by a desire to find someone to blame for this terrible accident, simply for the sake of doing so".

The Crown Prosecution Service (CPS) said it sought evidence from experts and eyewitnesses before making the decision to charge Mr Counsell.

The court had previously been told the smog was so thick that motorists on the northbound carriageway likened it to having a tin of paint thrown over their windscreens.

He said the prosecution's case was "heavily weighted" on "hindsight" and there was not sufficient evidence to show that Mr Counsell ought to have foreseen that smoke from the display could have drifted and mixed with fog to create thick smog.

"I have therefore concluded that the evidence is such that the jury cannot continue in these circumstances and it is my duty to stop the trial and order an acquittal," he added.

Mr Counsell, who ran Firestorm Pyrotechnics, was the contractor hired by Taunton Rugby Club to run the £3,000 display, which was watched by about 1,000 people.