PKR-linked NGO Invoke's adviser Rafizi Ramli today warned his critics that they were straddling a very "thin line" by arguing about the morality of offering cash prizes to encourage registration of new voters.

The PKR secretary-general singled out Bersih chief Maria Chin Abdullah and Centre to Combat Cronyism and Corruption (C4) executive director Cynthia Gabriel, both of whom have criticised Invoke's registration incentive.

"My point is this: It is a very thin line to argue along that line (morality).

"Especially more so if you are from an NGO perspective. Because it is common for NGOs like C4 and all - I am not sure about Bersih - it is common that we (NGO) get grants because we champion specific campaigns," he told reporters at Menara UEM in KL Sentral, after a meeting with top officers from Khazanah Nasional Berhad.