“People are entitled to questions … You cannot let doubts about the integrity of ministers fester and be left unaddressed. I have nothing to hide,” he was quoted as saying by TODAYOnline.

Balakrishnan said he was “very glad” that the prime minister agreed to the probe “and to publish all relevant facts and findings before we have a full debate in parliament”.

The two ministers are tenants of two separate colonial-era bungalows in the central Holland Village district.

Their tenancy first became a matter of social media chatter early in May after Kenneth Jeyaretnam of the opposition Reform Party wrote commentaries questioning whether the two ministers were “paying less than market value” for the properties.

The Workers’ Party, Singapore’s dominant opposition party, last week said members of the public had expressed concerns and that its MPs were filing legislative questions over the matter for the next parliamentary sitting in July. Lawmakers from the ruling People’s Action Party had also filed questions on the matter for the sitting.

In a four-paragraph statement, the Prime Minister’s Office said Teo Chee Hean, a senior minister and the coordinating minister for national security, had been tasked to “review the matter, and establish whether proper processes have been followed, and if there has been any wrongdoing”.

“This must be done to ensure that this government maintains the highest standards of integrity,” Lee said in the statement.

Teo, a veteran in the cabinet who is one of Lee’s most trusted aides, will “carry out the review expeditiously and to make the findings public in time for the Parliamentary sitting” in July, Lee added.

Lee said the two ministers in question had spoken to him requesting a review that was independent of the ministries and agencies they supervised, and that he had also asked for reports on the matter from the relevant agencies last week.

Amid public chatter over the issue, the Singapore Land Authority (SLA) – a statutory board under the Ministry of Law headed by Shanmugam – had said the two properties on Ridout Road were tenanted to the ministers above the “guide rent”, and that this was fully compliant with its procedures.

TODAYOnline said 31 Ridout Road, rented by Balakrishnan since October 2019, had a land area of 136,101 sq ft – about the size of two standard-sized football fields.

Information on the property at 26 Ridout Road – rented by Shanmugam since June 2018 – could only be found within a lot that included 24 and 31 Ridout Road, with a total land area of 525,171 sq ft, TODAYOnline said.

The SLA statement said the property currently tenanted to Shanmugam had been vacant for more than four years before he bid for the property. In the case of Balakrishnan, the property had been vacant for six years before it was tenanted to him.

Some critics say the controversy has emerged at a particularly inconvenient moment for the PAP, as it grapples with public unhappiness linked to concerns about housing affordability and availability.

“For the ruling PAP, coming at a time when many Singaporeans feel priced out of a red-hot property market, and when many are questioning the city’s gross wealth inequalities, this is a public-relations nightmare,” Sudhir Thomas Vadaketh, the editor of the independent digital magazine Jom, said in a Facebook post.

Singapore’s ministers are among the world’s highest paid, with the prime minister earning an annual salary of S$2.2 million (US$1.6 million) while an entry-level minister draws a S$1 million salary. Shanmugam, formerly one of the country’s top litigators, has been a minister since 2008. Balakrishnan, an eye surgeon who once served as CEO of the Singapore General Hospital, has been a minister since 2001.

In the city state, even mere questioning of possible impropriety by PAP ministers is rare and has in the past been met with fierce resistance. The ruling party, co-founded by Lee’s father Lee Kuan Yew – the country’s revered independence leader – prides itself on its zero-tolerance stance on corrupt practices within its ranks.

In 1996, following public chatter over the purchase of condominium units at a discount by Lee Kuan Yew and son Lee Hsien Loong, then the deputy prime minister, the elder Lee went to parliament to defend himself even though no formal charges were made against either of them.

Lee Kuan Yew, a senior minister at the time, himself brought the matter up in parliament, and then prime minister Goh Chok Tong – who probed the matter – said the facts proved that the Lees’ purchases were completely above board. Following the controversy, the Lees donated the amount of the discount to charity.