"The chief minister should realise the importance of the issue and take action against those involved in manipulation of marks," Leader of the Opposition and NPP leader Conrad K Sangma told reporters.
"It will set a bad precedent to defend the guilty and the chief minister will be responsible if he does not take action," he said.
Criticising Sangma for seeking a report from the chief secretary on how CBI report was leaked to the media, Conrad said the chief minister should "avoid shooting the messenger."
The CBI report named some ministers and legislators whose recommendations were taken into consideration while selecting candidates for the post of assistant teachers in government lower primary schools two years ago.