"From a legal point of view, the basic law and observations from practionners of law and international law do not allow the holding of a referendum on Palestinian soil," Ismail Haniya told a news conference on Sunday in Gaza City.
The statement by Haniya was the strongest sign yet that Hamas will not give in to Mahmoud Abbas's ultimatum to accept the plan, which calls for compromise with Israel.
Abbas has given Hamas until Tuesday to decide or face a national referendum.
Hanya's political adviser told al-Jazeera.net that the Palestinian premier had referred to the fact that "the basic law does not provide anywhere in its articles for the holding of referendums".
"Moreover, it is not among the president's prerogatives to call for referendums," Ahmed Yussuf said.
Yussuf also said that the Hamas-led government objects to holding a referendum less than four months after the Palestinian people elected it to replace Abbas's Fatah movement at the helm.
"The Palestinian people were sounded for their political opinion less than four months ago and chose Hamas," he said. "There is no need to ask them again [what they want] in a referendum."
Nevertheless the prime minister conceded that "from a political point of view, the holding of a referendum necessitates serious studies".
Yussuf said the plan should be put to a parliamentary vote.
"Abbas's proposal for a referendum came as a complete surprise. He didn't even consult the prime minister before the announcement," he said.
Abbas told Palestinian factions on May 25 that they had 10 days to accept the so-called prisoners' initiative or he would put the blueprint to a referendum within 40 days.
Cross-party talks, which have focused on the document drafted by jailed Palestinian leaders - among them Hamas militants - as a means to end deadly feuding between Hamas and Fatah, plus a financial crisis, are to conclude on Monday.
Hamas has so far refused to accept the blueprint, which among other things calls for a national unity government and the creation of a Palestinian state on land seized by Israel in 1967.
Hamas acceptance of the document could be seen as implicit recognition of the Jewish state.
Hamas says that an Islamic Palestinian state with Jerusalem as its capital must be established on the occupied West Bank, Gaza Strip and the territory on which Israel was founded in 1948.
But in the draft government programme posted on the group's website in March, the group said it believed that the issue of recognising Israel was a matter for the Palestinian people to decide, not merely one faction or another.
Abbas has asked the former parliament speaker, Rawhi Fattuh, and a businessman, Munib al-Masri, to meet Haniya "to ask him for his final position on the prisoners' document", his spokesman said.
"The only way forward for us, if the dialogue fails, is the referendum," Nabil Abu Rudeina said.
"The dialogue was for 10 days ... The political and economic situation is very bad in the Palestinian territories and we must find a solution."
Qais Abdul Karim, the representative of the Democratic Front for the Liberation of Palestine (DFLP) in the cross-party talks, suggested that if Haniya gave a positive response, the talks could continue in Gaza on Monday.
"If it is a negative answer, there is one way for Abbas. He must call a referendum," the DFLP official said.