Opposition parties fear Prime Minister Najib Abdul Razak's state visit to China may cost them at the polls, said Communications and Multimedia Minister Salleh Said Keruak.

"The opposition is worried that the China visit may sway some opposition voters and fence-sitters.

"So this Tuesday they are planning for Dr Mahathir Mohamad to make a 'guest appearance' in Parliament to distract Malaysians and divert attention away from the China visit," said Salleh in a post on his blog today.