In a tit-for-tat move, former law minister Zaid Ibrahim is offering RM10,000 as prize money for the best essay on Najib Abdul Razak being the country's "worst prime minister".

"I'm offering RM10,000 for the best essay on Najib as the worst PM this country has ever had. Other terms and conditions apply," he tweeted this afternoon.

Zaid's offer comes in the wake of Umno information chief Annuar Musa's announcement that RM10,000 would be presented for the best essay or social media posting on DAP leader Lim Kit Siang.