KUALA LUMPUR (Reuters) - Malaysia's veteran former leader Mahathir Mohamad returned from an overseas trip on Wednesday saying he would comply with any police investigation into comments he made against Prime Minister Najib Razak at an anti-government rally last month.
Mahathir has led calls for Najib's resignation over alleged mismanagement and corruption at indebted state investment fund 1MDB.
The strong stand by Mahathir, and Najib's actions to stifle dissent in the ruling United Malays National Organisation (UMNO) has raised fears of a split in a party that has led every government since Malaysia gained independence from colonial rule in 1957.
The political uncertainty has nagged at investor confidence in an economy whose ringgit currency has lost 19 percent of its value against the dollar so far this year, and is down to levels unseen since the Asian financial crisis 17 years ago.
The 90-year-old Mahathir surprised many in UMNO, as well as the opposition parties, when he joined tens of thousands of protesters in a two-day rally in Kuala Lumpur, organized by anti-corruption activists last month.
Speaking at the rally, which was declared illegal by city authorities, Mahathir called Najib a corrupt leader and said the people did not want him.
Malaysian police have said those comments warranted investigation, but the country's longest-serving prime minister remained defiant.
"(Let them) investigate....that's their job," Mahathir told reporters and dozens of supporters gathered at the airport to receive him on his return from a private trip to Jordan.
When asked about the possibility that he could be arrested for exercising his constitutional rights, Mahathir said: "I don't think they should, but I will comply."
Najib is faced with the biggest crisis of his political career following media reports of a mysterious transfer of more than $600 million into an account under his name.
Najib has denied any wrongdoing and says he did not take any money for personal gain.
But with the scandal refusing to die down, the prime minister has tightened his grip on power through a series of steps to sideline dissenters and muzzle critical media.
(Reporting by Emily Chow; Writing by Praveen Menon; Editing by Simon Cameron-Moore)