The report, compiled by Europe Economics, claims that government research is built on a number of unlikely assumptions and uses poor evidence to support its assertions.
ACS chief executive David Rae said: "If the government was planning to press ahead with liberalising laws on the basis of this report, we would urge them to think again."
Rae argues that the government's report, carried out by Indepen, does not properly assess the impact of changes on the small store sector, or assess the social consequences of local shops closing down.
The government is expected to decide in the next few weeks whether to proceed with changes. Any legislation would have to follow further consultation and full debate in both Houses of Parliament. So far more than 260 MPs have signed an Early Day Motion opposing liberalisation.
The analysis was also criticised this week during an adjournment debate in the House of Commons on Sunday Trading by Andrew Smith MP. He was angry that the research did not consider arguments such as Sunday being the Christian day of rest, or protection for staff unwilling to work.