"This is a coup," Barhoum said on Saturday.
Palestinian security officials have accused Israel of violating a fragile ceasefire in Gaza, saying that an Israeli navy vessel fired on Palestinian fishing boats on Saturday
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"We cannot accept such a step, which is against Palestinian democracy and goes against the election results. The PLO doesn't represent the Palestinian people."
Ismael Haniyah, the Palestinian prime minister, who left last week for a tour of the Arab world, has told Mahmoud Abbas, the Palestinian president and head of Fatah, that in the past he would only step down once agreement had been reached on a new government.
On Saturday, Abbas met with a string of European dignitaries in Gaza to brief them on the internal disagreements among the Palestinians and a nascent truce with Israel in the Gaza Strip.
EU foreign policy chief Javier Solana said the collapse of unity government talks took with them any hopes of ending the international economic sanctions on the Palestinian government.
After meeting with Abbas, Solana accused Hamas of missing its opportunity to form a unity government.
"Very sadly, I have to say the chance has been lost," said.
The executive committee of the Fatah-dominated Palestine Liberation Organisation has called on the Hamas-led government to resign so a new government can be formed.
The body met on Friday after Abbas declared that talks with Hamas on forming a unity government were dead.
"The Executive Committee stressed the necessity of implementing this step before beginning any new dialogue over a new government," a statement said.
Abbas has the authority to dismiss the Hamas government, but has been reluctant to do so because any new cabinet would need to be approved by the parliament, which is dominated by Hamas.