The imprisonment of former prime minister Najib Abdul Razak will not cleanse Umno of its corruption-tainted image, said Pejuang chairperson Dr Mahathir Mohamad.

According to Mahathir, himself a former prime minister and former Umno president, corruption in Umno has cascaded down to the grassroots level.

This is the reason, he said, why the party should be completely...