His statement, released Tuesday, followed speculation that Pakatan Rakyat, led by Opposition leader Datuk Seri Anwar Ibrahim, was attempting to forge a unity government with its political rival.
"The PAS central committee previously, is a series of meetings recently, has stressed that there is no longer unity government talks with Umno.
"This decision was made by PAS president Datuk Seri Abdul Hadi Awang and was agreed on by the central working committee," said Nasrudin.
He said the president had already reviewed the need to form a unity government after the 2008 general election, before rumours of a unity government involving Anwar surfaced recently.
"But I would like to take the stand that the party had made for the longest time (which is to reject the idea of unity government.)
"I believe my friends in PAS and outside the party will share similar sentiments as we have agreed to stay in this pact together," he said.
Nasruddin, who is also Temerloh MP, also said the Islamist party should learn from past mistakes, when it formed a unity government with Umno in 1970.
"Therefore, we won't allow anyone to drag us into any action that will put our principles and policies at risk," he said.
He added if PAS wanted to take part in a unity government, the matter had to be approved by its highest decision-making body, Syura Ulama council.
"And it is not appropriate for any PAS leader to pre-empt anything, in order to prevent similar conflicts from happening again," he said.