Negeri Sembilan Bersatu chief Rais Yatim said today those who wish to talk about politics should join politics.

Rais said this after noting that Johor Crown Prince Tunku Ismail Sultan Ibrahim has touched on the topic a lot.

"TMJ (Tunku Ismail) talks a lot about politics. Please stop the innuendo about wanting to replace the prime minister. That is the right of ordinary citizens.

"If (one) wants to talk about politics, please register a political party," he said in a Twitter posting.

Rais, a former minister, said the realm of royalty and politics should not mix.

"The realm of rulers is different. The realm of politics is different. Do not mix them according to the whims of a prince.

"It may cause unrest among the people. Please be rational," his tweet read.

After Tunku Ismail's football club Johor Darul Ta'zim's (JDT) lost to Shandong Luneng in an AFC Champions League match on Wednesday, he appeared to make a snide comment against Prime Minister Dr Mahathir Mohamad.

Read more: Dr M to TMJ: Only rakyat can decide who will be PM

Fans along the road chanted "Hidup TMJ (Long live TMJ)" as the prince's black SUV drove by, but one shouted "change Mora," in reference to JDT coach Benjamin Mora.

The vehicle ferrying Tunku Ismail then came to a stop, before he stuck his head out the passenger side window and said "Instead of changing Mora, it's better to change the prime minister," which courted laughter from JDT fans.

Mahathir, in a press conference in Beijing this afternoon, responded by saying that the Johor crown prince has been changed before, but only the people can change the prime minister.

Mahathir did not name names, but appeared to be referring to Tunku Ismail's grandfather Sultan Iskandar Sultan Ismail, who was stripped of his crown prince title due to behavioural issues, before it was restored.