“I really don’t understand it.

“If there was nothing to worry about, there is no need for PH leaders to issue statements proclaiming there is nothing to be concerned about,” the former prime minister said in a Facebook post.

Najib went on to say that it would be better for PH to focus on the ailing economy, the increase in the cost of living and the billion ringgit Penang undersea tunnel scandal.

Prime Minister Dr Mahathir Mohamad had said over the weekend that he was not worried about the cooperation between the two parties, which he said led to Barisan Nasional’s victory in the Semenyih by-election on Saturday.

Today, in a blogpost, Mahathir claimed that the alliance was geared towards ensuring Najib’s return as a leader and absolving him of his alleged crimes.

PKR president Anwar Ibrahim also appeared unperturbed over the cooperation between Umno and PAS, saying not all Malays supported the two parties.

Yesterday, at a joint press conference with PAS’ top leaders, Umno’s acting president Mohamad Hasan announced the formalisation of cooperation between the two parties.

Describing their cooperation as a “marriage”, Mohamad said Umno and PAS would work together as a united opposition bloc in Parliament and in future by-elections.

Today, PAS declared that it would help Umno’s candidate win the Rantau by-election, which will be held next month.