"The EIP is an important policy that is applied to all ethnic groups consistently," Mr Wong said in Parliament yesterday.
He was responding to Mr Lim Biow Chuan (Mountbatten), who had proposed helping non-Chinese flat owners avoid "the squeeze" of the EIP's effect on prices.
His ministry, however, will consider a suggestion from Mr Saktiandi Supaat (Bishan-Toa Payoh GRC) to put out monthly guidelines on how much flats affected by the EIP could sell for.
The duo were among four MPs who expressed concerns about the EIP, saying that while it is useful in promoting racial harmony, the policy has affected their residents' ability to sell their flats quickly or at market value.
The EIP specifies the proportion of units in a Housing Board block and precinct that can be owned by a particular racial group.
It was implemented in 1989 to ensure a balanced mix of ethnic groups living in HDB estates, in a move to promote racial harmony and strengthen social cohesion.
Number of requests to waive the ethnic quota rule that the HDB received between 2015 and last year - higher than the 1,200 appeals received between 2013 and 2015.
But some minority home owners have complained the EIP makes it difficult for them to resell their flats and, last month, three of them wrote to The Straits Times' Forum page, spelling out their difficulties.
Between 2015 and last year, the HDB received 1,600 requests to waive the quota rule, Mr Wong said when replying to Mr Pritam Singh (Aljunied GRC). But he did not say how many appeals were successful.
The figure given yesterday is higher than the 1,200 appeals received between 2013 and 2015, according to statistics disclosed previously by the ministry. Four in five of those appeals were not successful.
But the EIP is not the sole factor in the sale of a flat, Mr Wong said. "While home owners may have their own expectations of how much their flat can sell for, flat attributes such as location, storey, physical condition of the flat, remaining lease and market sentiments would also be considered by prospective home buyers," he added.
As for residents, especially the elderly, who face difficulty in selling their flats for months or years, Mr Wong said any help by the ministry would be given on a case-by-case basis. But "we have seen recent transactions within that same neighbourhood", he added in his reply to Mr Chong Kee Hiong (Bishan-Toa Payoh GRC).
Still, the HDB may give more time to those struggling to sell their flats and advise them to be realistic about their asking prices, he said, adding that it will "continue to exercise flexibility for households with exceptional circumstances".