"A Singapore diplomat attended the (National Justice Party) Keadilan briefing as part of his duties to follow political developments in Malaysia," a foreign affairs spokesman said.

"Attending such briefings given to several diplomatic missions by a legal opposition party represented in Malaysia's parliament is part of the routine work of a diplomatic mission."

Malaysian Prime Minister Mahathir Mohamad had criticised Singapore, Indonesia, the United States and several other countries whose diplomats attended the Apr 5 meeting called by Wan Azizah Wan Ismail, who heads the National Justice Party.

"They should be sensitive to our feelings and not interfere in our domestic affairs," Mahathir said.

Wan Azizah had called the meeting to discuss the health of her husband, jailed former deputy premier Anwar Ibrahim, who has acute back pain due to a slipped disc and has been denied permission to go overseas for an operation.

The Singapore foreign ministry statement said attendance at the meeting did not signify support for the opposition party.

It was important for Singapore and Malaysia to understand developments in the other country and "this must necessarily entail contacts" with players inside and outside the government, the Singapore spokesman said.

"This should not be regarded as interference so long as diplomatic conventions are respected."