The current small business rates relief (SBRR) scheme is "grossly unfair", an SME lobby group claims.
The Forum of Private Business (FPB) said the rate relief criteria needs an overhaul and not enough effort is being made to raise awareness of firms' entitlements.
Recent research by the Local Government Association revealed that less than half of the 870,000 small businesses across England eligible for the scheme have applied for it, meaning they are potentially missing out on rate relief of up to £2,500 per year.
FPB research analyst Andy Mowlah said the level at which a business is entitled to SBRR must be increased because many firms with low turnovers miss out because they require larger turnovers due to the nature of their business.
"Take for example a second hand car lot," he said. "The owner needs larger premises than, say, an online retailer but could have a considerably smaller turnover.
"Under the current system, the smaller premises with the greater turnover is entitled to claim relief, but the car dealer is not.'
The government's consultation on reducing the administration involved in the scheme ends today.