On Saturday, Mushir al-Masri, a Hamas legislator, warned Shalit's parents that Israel was jeopardising their son's life by not agreeing to release the Palestinian prisoners.
"We emphasise to the Shalit family that [Israeli Prime Minister Ehud] Olmert and the people around him are gambling with their son's case," al-Masri said in a statement posted on a pro-Hamas website.
"He will remain with us and we will negotiate over his bones"
Moussa Abu Marzouk, Hamas political bureau deputy head
"Shalit will not see the light of freedom and will not see his mother and father as long as our prisoners remain in jail."
Abu Marzouk also told the Kuwaiti newspaper from his base in Damascus, Syria, that Hamas would support early legislative elections, reversing the group's long-standing opposition.
Hamas trounced the rival Fatah group in parliament elections in 2006 and had previously opposed holding new contests before the end of the normal four-year term.
Khaled Meshaal, Hamas's political chief, recently said that Shalit was alive and being treated well.
Shalit was seized from an army base near Gaza by fighters from three groups including Hamas, which evicted the Fatah group led by Mahmoud Abbas, the Palestinian president, from the territory in a week of bloody clashes last June.
Hamas had initially demanded the release of 450 Palestinian prisoners but Israel said some of them had been involved in attacks that killed Israelis.
Meanwhile, a Palestinian boy was shot dead by Israeli tank fire in the Hamas-ruled Gaza Strip on Sunday, according to Palestinian medical sources.
One person was wounded in the attack between the Bureij refugee camp in central Gaza and the border with Israel, the sources said.
An Israeli army spokeswoman said a ground force carried out an incursion aimed at "distancing terrorists from the [border] fence" following several Palestinian shooting attacks from the area.
Since Israel and the Palestinians formally relaunched peace talks in November at least 368 people have been killed, most of them Gazans accused by Israel of being fighters, according to an AFP count.