Zaid, who arrived at Bukit Aman at 9.30am, was questioned for about an hour.

When met by reporters outside the police headquarters, he said the questioning had been carried out in a professional manner.

“They (the police) were professional and they asked me relevant questions.

“This is solely about the tweet in which I cautioned the sultan about his statement,” he said.

He was referring to Sultan Sharafuddin Idris Shah’s remark that Mahathir’s political agenda was motivated by “deep hatred” and that “his anger will burn the whole country”.

In response, Zaid had tweeted: “The Selangor sultan should be careful with his words. No one is immune when the country burns.”

Zaid’s comment caused an uproar, especially among Umno leaders and members who called for action to be taken against him for his criticism of the sultan.

However, Zaid said he had explained to the police that the tweet was his response to the ruler about Mahathir’s statement.

“I explained that it was my own opinion and not the opinion of any other groups, parties or the opposition.”

He said he had also told the police it was important that the country and its democracy be defended.

“I felt I was responsible to explain the duties of the constitutional monarchy, and how we have to defend the country and its democracy and understand what needs to be done by everyone.

“They mentioned that if it’s needed, they will call me up again, which is normal as the police can call you up any time.

“I told them I’m not going on any leave, so I can come any time they need me to.”

Zaid was accompanied by legal counsel Amarjit Singh Sidhu and DAP leaders including Ronnie Liew and Segambut MP Lim Lip Eng.