The Israeli government is not serious about a planned deal to swap prisoners with the Palestinian group Hamas, an ex-Israeli official claimed Sunday, casting doubt on whether Israel would seek to free Israelis held captive in Gaza.

Moshe Tal, who was a top negotiator for Israel's missing soldiers in Gaza, told the local Radio 103FM that he had resigned his post after he felt that the Israeli government was not serious about seeking the return of Israelis held in Gaza.

He added that the Israeli authorities had missed several opportunities to retrieve Israelis held by Hamas in Gaza, citing that there was an opportunity to reach a prisoner swap with Hamas one month after the Naftali Bennett government came to power.

Egypt is leading mediation talks between Israel and the Hamas group, which rules the Gaza Strip, in an effort to reach a prisoner swap agreement. No progress, however, has been made so far.

Hamas, which rules Gaza, keeps four Israelis captive, including two soldiers captured during the Israeli war on the territory in the summer of 2014. The other two are civilians who entered Gaza under unclear circumstances.

The Palestinian group, which has not disclosed information about the conditions of the four Israeli hostages, demands the release of Palestinians in Israeli prisons in exchange for Israelis in captivity.

An estimated 4,600 Palestinians are believed to be held in Israeli prisons, including 41 women, 140 minors and 440 administrative detainees, according to data compiled by organizations defending the rights of prisoners.