Prime Minister Datuk Seri Najib Tun Razak warned parties against defaming him and his family in connection with 1Malaysia Development Berhad (1MDB).

He expressed regret that a report by a newspaper which was the official voice of the opposition had published a false report on Feb 19 and described the article as irresponsible and a lie.

"Indeed what is written in the HarakahDaily article "Dana 1MDB biayai syarikat filem Riza Aziz (Bhg 2) (1MDB funds finance Riza Aziz film company (Part 2)) that was published on Feb 19 was a slander by irresponsible parties that was nothing more than lies, not based on facts and had no concrete evidence.

"As a citizen of this country Malaysia, I have the right to defend myself and my family from bad slanders using the legal system of the country," he said, in his Facebook on Friday.

Najib said he had ordered his lawyer to take legal action to summon the opposition newspaper to retract the article.

"I wish to stress here 1MDB is a strategic development company owned by the Malaysian government and I will definitely not allow anyone to use or misuse any public funds for personal interests or profits," he said.

He said as prime minister, he was prepared to receive constructive criticisms but "would not stay quiet or compromise if wild allegations that were baseless were being hurled at his family."

Yesterday, Najib had submitted a letter of demand to HarakahDaily on the defamatory statement in the article on the 1MDB funds in its website.

It was handed over to Harakah managing director Dr Rosli Yaakop and HarakahDaily editor-in-chief Taufek Yahya.

According to Tetuan Hafarizam Wan & Aisha Mubarak, the legal firm that represented Najib, the letter of demand was filed in his personal capacity based on the report Dana 1MDB biayai syarikat filem Riza Aziz (Bhg 2) on February 19.