PKR vice-president Rafizi Ramli has challenged Prime Minister Najib Abdul Razak to sue him if he was wrong about the cost for the Mass Rapid Transit (MRT) project.

"I challenge Najib to sue me in court within seven days if it is true that the total cost of the 150km MRT project does not exceed RM100 billion.

"If he does not file the lawsuit within seven days from today, I want him to apologise to the rakyat for his confusing statement that (the MRT project) successfully saved RM2 billion," Rafizi said in a press conference in Kuala Lumpur today.