Labour called on the Government last night to consider shelving plans to raise the motorway speed limit to 80mph as police continued to investigate the cause of the M5 crash on Friday in which seven people died.
Two lorry drivers working for a family-run food company were named among the fatalities in the UK's worst road accident for 20 years.
Avon and Somerset Police Assistant Chief Constable Anthony Bangham confirmed that the smoke cloud said to have been generated by the Taunton Rugby Club fireworks display was a "significant line of inquiry".
But Justine Greening, the Transport Secretary, told the Commons it was "far too early to jump to conclusions over causes" and warned that police might not reach a definitive view of the cause.
In September, Ms Greening's ministerial predecessor, Philip Hammond, announced a consultation with a view to raising the national speed limit from 70mph to 80mph. Maria Eagle, the Shadow Transport Secretary, yesterday called on Ms Greening to fully consider the conclusions of the M5 investigation before "steps are taken to advance any proposals in her department that may affect road safety".
Ms Eagle also called for a review of licensing policy for fireworks displays and other activities close to motorways. The Department for Transport said fireworks displays must not take place within 50ft of a major road. Officials from Taunton Rugby Club maintain that the fireworks site was about 1,500ft from the carriageway and that essential safety checks had taken place.
Last night, Lee Waddon, the director of rugby at the club, said: "As a family orientated club in the heart of this community we would like to express our sorrow to so many lives which have been affected in such a horrific way."
All seven fatalities have now been named. Samworth Brothers, which owns the Cornish pasty maker, Ginsters, confirmed that two of its drivers were killed and a third seriously injured in the crash.
Terry Brice, 55, a father-of-five from Bristol, and Kye Thomas, 38, a father-of-four from Cornwall, were killed in separate lorries.
Mr Thomas served with the King's Royal Hussars before becoming a driver for Samworth Brothers.
Malcolm Beacham, 46, an event co-ordinator for a historical re-enactment group, from Bridgwater, Somerset, was also named as a victim.
Of the 51 injured, Musgrove Park Hospital in Taunton said eight people had been discharged and 11 were still being treated. The M5 has now been reopened in both directions.