The Housing Law requires commercial apartments to be at least 45 sq.m.
Developers can proceed with approval from local authorities except in case of large projects with 500 units and above, in which case they should also seek the ministry’s permission.
The ministry's move comes after real estate companies and experts proposed dividing unsold apartments into smaller ones to improve sales.
Saigon Times newspaper recently quoted Nguyen Van Duc, deputy director of Ho Chi Minh City-based property company Dat Lanh, as saying his company has been seeking permission since 2011 to divide 15 apartments of 102-242 sq.m into smaller ones after struggling to sell them.
Duc, also the deputy chairman of the HCMC Real Estate Association (HoREA), told Thanh Nien last year that developers had focused on the high-end and mid-priced segments while the majority of demand was in the lower end.
His company's apartments of less than 50 sq.m were selling fast, he added.
Le Hoang Chau, HoREA chairman, said earlier this month that the luxury segment accounts for most of the inventory, estimated at 48,500 units in HCMC and Hanoi as of last year by property services company CBRE.
This is priced out of reach of the majority of the population, he said. Last year Vietnamese earned $1,540 on average.
Besides the size, the ministry said developers are also allowed to change the their projects from commercial to social housing.