She was attacked in July and had about a litre of acid poured on her.
The 33-year-old died in November after months of treatment, including more than 10 operations.
Her murder sparked shock and uproar with activists accusing the authorities of failing to complete the investigation or identify the mastermind.
On Monday, less than two months before Ukrainians go to the polls to elect a president, General Prosecutor Yuriy Lutsenko pointed the finger at the head of the regional council in the southern region of Kherson, Vladyslav Manger.
"It was he who ordered and partially organised this crime by financing it," Lutsenko told a news conference.
According to the charge sheet released by Lutsenko, Manger was guided by "personal animosity" because Gandzyuk opposed "illegal logging" in the region.
Lutsenko said the prosecution had obtained enough testimony from witnesses about Manger's role, adding that the attackers had received "no less than 4,000 dollars." In August, police detained five people, three of whom were placed under house arrest.
In November, a former aide to a ruling party lawmaker was arrested on suspicion of involvement.
Lutsenko's spokeswoman Larysa Sargan said Manger was accused of "intentionally and unlawfully causing the death of another person... with special cruelty and by prior agreement with a group of individuals".
Speaking to AFP, Sargan said Manger had not been arrested, adding: "Searches are under way in Kherson." If found guilty, the 48-year-old faces up to life in prison.
Manger insisted he did not know Gandzyuk personally and that he had no ties to her.
"I am ready to answer all questions from investigators," he said in televised remarks.
"I am not going to go anywhere and will fully cooperate with the investigation." On Tuesday, a Kiev court is expected to consider a request from the prosecution to formally arrest him.
He was expelled from the party last week.
Activists accuse police and prosecutors of dragging their feet, insisting the detention of those possibly involved only happened after a wave of protests across the country.
Lutsenko in November submitted a letter of resignation to Poroshenko but the Ukrainian leader refused to fire him.
More than 50 attacks on anti-graft activists, environmental and human rights campaigners including five murders were recorded last year.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)