Analysis of the multiples' annual reports shows the two firms added 2.75 million square feet of selling space last year, but their collective workforce fell by 426 employees.
Speaking at this month's ACS Summit, ACS chief executive James Lowman said multiples were using their job creation claims to argue for an easing of out-of-town planning laws in the Localism Bill.
"Supermarkets are promising more jobs than can be delivered to secure permission for new out-of-town retail parks," he added.
"Without clauses in the Bill to support sustainable high streets, communities could be left at the mercy of the big developers who could use the crisis as a way of forcing through plans for big out-of-town stores which would have a devastating effect on the long-term prospects of high streets."
Also speaking at the Summit, Devon retailer Lesley Brown, who is facing competition from a new Tesco, said many councillors involved in making decisions on supermarket planning applications weren't fully aware of the employment implications.
"I'm sure that many councillors don't understand the issue," she told delegates at the Summit's Local and Vocal breakout session. "For example, on paper the new store is creating 500 jobs, but there were already 150 jobs in the existing premises before Tesco took over, and what about job losses caused when other stores go out of business?"
Phil Ponsonby, chief operating officer for food retail and services at Southern Co-operative, urged retailers to "build a relationship with councillors now, not when the issues arise".
Jonathan James, who runs three Spar and three Budgens stores in Cambridgeshire, added: "We need to make councillors more aware of the issues."
ACS public affairs director Shane Brennan said: "You've got to get your voice heard, otherwise people who don't agree with how you do business will be shouting louder than you."