Deputy Prime Minister Muhyiddin Yassin said today he believed that the "slander mills" of the opposition political parties would operate round the clock in the final phase of campaigning in the Hulu Selangor parliamentary by-election, polling for which is on Sunday.

He said the opposition was beginning to feel pressured and would resort to anything, including circulating slanderous leaflets against Umno and Barisan Nasional (BN) leaders.