Asda will pursue legal action to prevent a proposed five-day strike by workers at its distribution depots around the UK.
Asda employees who are members of the GMB union have vowed to walk out next Friday. But the Leeds-based supermarket chain will seek an injunction against the strike, citing "serious irregularities" in the ballot.
"There were serious flaws in the ballot process with people who don't even work for Asda being sent ballot papers," said Asda's people director David Smith.
"We have tried raising this with the union but they have ignored us.
"With only one per cent of our colleagues voting for a strike, we've got to do all we can to protect the other 99 per cent."
A GMB spokeswoman said it was taking legal advice and would make no immediate comment.
