Motorists trapped in the Haymarket car park because the steep exit ramp had not been gritted decided to do it themselves.
Seven members of the public got shovels from cleaning staff at the centre and used them to clear the snow and distribute grit from a bin near the ramp.
They acted after being told they might have to leave their vehicles at the city council-run car park overnight on Friday – and pay the extra charges.
A spokesman for the council said it had been aware of the problem, but its gritters had been caught up in the gridlock which brought the city to a grinding halt.
Janet Ellson, 74, of the Scraptoft Lane area of Leicester, was among those trapped, along with her son, Colin, who helped clear the snow and spread the grit.
She said: "When we got there at 3.50pm we were told it was too dangerous to drive down the ramp.
"A security guard said he had called the city council, but no-one arrived. He said we could leave the vehicles overnight, but would have to pay the extra charges!"
A spokesman for the council said: "We had all of our gritting teams out on Friday treating about 283 kilometres of roads. We did get a call to go to the Haymarket, but the team were caught up in the congestion and did not make it until after the drivers had gone."
