Non-resident ambassadors, ambassadors-at-large and special envoys are not civil servants, and are hired for a specific role, Minister for Foreign Affairs Vivian Balakrishnan said in Parliament yesterday.

They are expected to safeguard and advance Singapore's national interests, explain and defend the country's policies, and uphold its integrity and reputation, he added.

But beyond these commitments, he said, the Ministry of Foreign Affairs does not restrict their private engagements, including the speeches they make and articles they contribute in their personal capacities.

Dr Balakrishnan was responding to Non-Constituency MP Leon Perera, who asked if there are guidelines on the public speeches and writings made by people in such positions.

Mr Perera was referring specifically to Ambassador-at-large Bilahari Kausikan and his comments on Malaysian politics in an opinion piece published in The Straits Times last October. The commentary was criticised by Malaysian opposition politicians.

Mr Perera asked if such comments were permissible, adding they could impact diplomatic ties.

The minister said Mr Kausikan is a retired civil servant, whose speeches "do not reflect or represent, nor does he even attempt to say that they are, the positions of the Singapore Government".

Mr Kausikan, a former permanent secretary at the Foreign Ministry, retired in 2013. Said Dr Balakrishnan: "He's free to speak and comment in the same way you are free to speak and comment as a private citizen."

He added: "I do not want to open up this House into an avenue for any member, regardless of which party you're from, to discuss the writings and the speeches of other private citizens of Singapore."