"The Cabinet decision (to approve the Gaza pullout) offers Hamas a terrorist state on a plate, at the expense of the blood of Jews," Housing Minister Eitam charged in his letter on Tuesday to Sharon.
A party colleague and deputy social affairs minister, Yitzhak Levy, also submitted his resignation in protest against the Cabinet's decision on Sunday to approve Sharon's so-called disengagement plan.
"The flag of the Land of Israel has been lowered to half-mast in your days," Levy wrote in his resignation letter to Sharon.
But another of the NRP's six deputies, Welfare Minister Zevulun Orlev, has decided to remain in the Cabinet.
Public radio said that despite Eitam and Levy's exit from the government, the NRP would continue to support Sharon's coalition.
Their departure comes just days after Sharon sacked two members of another party which supports Jewish settlement on Palestinian land, the National Union.
While their dismissal ensured him a victory in cabinet on Sunday, it left him with the theoretical support of just 62 of the 120 deputies in the Knesset.
"The flag of the Land of Israel has been lowered to half-mast in your [Sharon's] days"
National Religious Party minister
Eitam has savaged the Cabinet decision to back Sharon's disengagement plan, which envisages the evacuation of all 21 of the settlements in the Gaza Strip and another four isolated enclaves in the northern West Bank, as "one of the blackest decisions ever taken by the Israeli government".
No early pullout
Sunday's agreement stipulated that no pullouts from Gaza would take place before March 2005 at the earliest and each phase of the evacuation process would be subject to a separate vote in parliament.
Senior figures in the party had called for the ministers to remain in place for at least the next three months in order to oppose the plan from a position of strength.
All Israeli settlements in the occupied territories of West Bank and Gaza are considered illegal under international law.
Sharon's disengagement plan envisages giving up parts of the Gaza Strip and seizing more land in the West Bank.