Though there was no official word on it from Raj Bhavan, Tamizhaga Vazhvurimai Katchi led by T Velmurugan claimed Purohit had sent the cabinet's recommendation to the Centre, calling it against the Constitution and a "slight" to Tamil people.
A former MLA, Velmurugan said it was only to avoid legal complications that their release was contemplated under Article 161 of the Constitution by the state.
The Supreme Court had also disposed of a related case recently which was earlier a "stumbling block" in freeing the convicts, he said.
Disposing of a petition by the Centre, the Supreme Court had said on September 6 that Tamil Nadu governor was at liberty to decide the mercy petition of A G Perarivalan, one of the convicts.
Under such circumstances, he said, the governor should "give his approval for the release of the convicts and abide by the law ".
To urge the governor to accord his approval and go by the law, his party would hold a "besiege Raj Bhavan" protest on September 26, he said.
When approached to ascertain whether Purohit has forwarded the state's recommendation to the Centre, a Raj Bhavan official said, "It's confidential and we cannot comment on it".
Tamil Nadu Law Minister C Ve Shanmugam said there was no formal word on it.
"There is no official communique on it," Shanmugam said in a terse reply.
"Under Article 161, the governor of a state has full powers to decide on the recommendations of the state Cabinet,"
the minister said on the sidelines of a function in Cuddalore.
Tamil outfit "Tamil Desiya Periyakkam" said the governor sending the recommendation to the union home ministry raises suspicion if he was succumbing to "North Indian political pressures".
Under Article 161, the governor cannot exercise his personal discretion and has to just implement the Cabinet's decision, it said.
DMK organising secretary and Rajya Sabha MP R S Barathi backed the release of the convicts and said he felt there was no need to take up the matter with the Centre.
"In my opinion, sending the recommendation to the central government is not necessary. The Supreme Court's direction should be followed," he told PTI.
When the Supreme Court has given its direction, the governor has to act accordingly, he said, adding it is "crystal clear" that the apex court has ruled that the state government can take a decision on the issue.
The state's ruling AIADMK, since the days of late J Jayalalithaa, has been for releasing all the seven convicts.
CPI state secretary R Mutharasan dubbed the governor's action as "delaying tactic". "It seems to have been done with the ulterior motive of denying them freedom," he said, adding the sentiments of Tamil people should be respected.
The Congress had, however, deprecated the state government's recommendation.
"There can be no compromise on terrorism and terrorists. The state cannot derelict its duty on punishing terrorists.
"There can be no politics over Rajiv Gandhi's assassins as SC hasn't granted any relief to them. It's time the government takes a cue and follows the same line,"
Congress spokesman Randeep Surjewala had said soon after the Tamil Nadu government made the recommendation.
While the mainstream parties and pro-Tamil outfits staunchly support the release, families of the victims of the blast in 1991 have opposed the move.
Coming together, the families of victims led by the coordinator of their forum S Abbas, whose mother was among those killed, have sought an appointment with the governor to present their views.
The Tamil Nadu government had said on Thursday it was confident that the governor will respect people's feelings which reflect in the cabinet's recommendation.
In its recommendation, the state cabinet said all the seven convicts--Nalini, her husband Sriharan alias Murugan, Perarivalan, Robert Payas, Jayakumar, Ravichandran and Santhan-- should be released.
Murugan, Santhan, Jayakumar and Payas are Sri Lankan Tamils.
All the seven convicts are serving life imprisonment and are behind bars since 1991.
Rajiv Gandhi was killed in a blast at an election rally in Sriperumbudur near here on May 21, 1991. Fourteen others, including Dhanu, the assassin, were also killed.