Opposition leader Anwar Ibrahim described Foreign Minister Hishammuddin Hussein's statement calling China a "big brother" to Malaysia as an insult to our non-aligned position.
Anwar said China is a friend and efforts should be made to improve trade and investment cooperation but said such language was inappropriate in international diplomacy.
"This is not the language or style that should be used in global diplomacy and international relations.
"It makes it look as if Malaysia is a foreign puppet," he said.
Hishammuddin, who ended his two-day working visit to China, had during a press conference with his counterpart Wang Yi, described China as Malaysia's "big brother".
Wang Yi responded by saying: "We are brothers". The exchange was reported by the state media in China.
Anwar said Hishammuddin's conduct deviated from Malaysia's decades-long position in international diplomacy.
"As a non-aligned nation that does not side with any major power, his (Hishammuddin's) statement is a clear form of insult on our country.
"The foreign minister should apologise to Malaysians and retract his tasteless statement," he added.
While Malaysia and China have seen increasingly strong ties, a few key issues remain.
This includes China's repeated encroachment into Sarawak waters which is recognised under international law.
However, China does not recognise the Exclusive Economic Zone that defines international maritime borders and claims most of the South China Sea as its own.
Meanwhile, a group of researchers also expressed concern that Malaysia describing China as a "big brother" will send a strong signal to other major powers and raise questions about the country's foreign policy direction.
"The use of such a term is inappropriate in Malaysia's foreign policy direction," they said in a joint statement.
The statement was signed by Research for Social Advancement research coordinator Fakhrurrazi Rashid, Strategic Studies and International Relations Researcher Group's Ahmad Muziru Idham Adnan and Universiti Malaysia Sarawak international studies alumnus Muhammad Ariff Mohamad Nizam.
They said Malaysia needs to be consistent in its non-aligned position to protect the national interest.
"The Foreign Ministry should explain to Malaysians the use of the "big brother" term as it could be interpreted as China being a protectorate of Malaysia and that Malaysia will bow to China.
"Both countries have various overlapping claims involving the issue of sovereignty," they added.