Karu Jayasuriya refused to identify the 'Joint Opposition' as an independent group in parliament separate from the United People's Freedom Alliance (UPFA).
"I have discussed the issue with my security personnel and they will be taking some action soon," Jayasuriya told parliament.
His remarks came in response to a query raised by an opposition legislator.
"In politics these things are not unexpected. I was not shattered by it," Jayasuriya said.
He said he had received death threats over telephoneon Tuesday nightfollowing his refusal to accept the group backing Rajapaksa as a separate entity in parliament.
The refusal sparked protests with Rajapaksa loyalists coming to the chamber well.