He told reporters covering his campaign sortie here that it was former Cebu governor Lito Osmeña, whose Promdi is part of Rocos three-party coalition, who negotiated for the former senator and education secretary.
He said its not true, as Osmeña claims, that it was his camp that approached Rocos group and proposed a merger.
"It was the other way around. It was Lito Osmeña who approached us. According to him, Senator Roco would slide down to become part of the merged senatorial ticket. I am forced to reveal this because they are altering the story of what really happened," Lacson said.
He said the Roco emissary met separately during the Holy Week with Makati Rep. Agapito "Butz" Aquino and with his political adviser and spokesman, Lito Banayo.
"Of course there was the usual concession relating to expenses in the vicinity of P100 million," Lacson said.
Asked what would those expenses be and if they would include reimbursements for amounts that the Roco camp already spent, Lacson said, "No reimbursement, the amount is for expenses of their senatorial ticket and local candidates."
"Of course, I and Rep. Caloy (Carlos) Padilla put our foot down. We did not want any concession or compromise. That is the reason why we have been going it alone. I am very comfortable with Caloy. Okay lang if people want to join us, especially those who share our cause. But if they want money, forget it," he stressed.
The former Philippine National Police chief hinted that Rocos handlers could have negotiated with President Arroyo after failing to obtain the supposed concession from him.
"To set the record straight, kami ang unang nilapitan. So we already expected Senator Roco last Sunday or Monday to withdraw (from the presidential race) in favor of Mrs. Arroyo. But he was stopped by some of his senatorial candidates from announcing support for the incumbent," he said.
Roco, who served as Mrs. Arroyos education secretary, announced last Tuesday that he was taking a leave from the campaign to get medical treatment in the United States for chronic back pain. Former health secretary Jaime Galvez-Tan, his campaign manager, said his candidate would be back in two weeks.
Lacson said it is also not true that his group is wooing former bowling champion Bong Coo, a Roco senatorial bet.
"Wala kaming nililigawan sa kanila," he said.
Lacson was welcomed in this northernmost town of Ilocos Norte by Mayor Marlon Sales, his brother Teteng Sales, who is running for congressman in the first district of this province, and his councilors.
The local officials all belong to the Laban ng Demokratikong Pilipino faction led by Lacson, Aquino and Padilla.
They are supporting a mixed Lacson-Loren Legarda ticket, in addition to Padilla and some Ilocano senatorial candidates, including former senator Heherson Alvarez, who comes from Isabela.
Legarda is the vice presidential running mate of Lacsons opposition rival, movie actor Fernando Poe Jr. Lacson does not have a vice presidential candidate.