The militant Hamas movement has launched a stinging attack on BG Group and vowed to block a potential £2 billion deal being brokered by the company to supply Palestinian gas to Israel.

The Islamist group told The Times that any agreement would be equivalent to a modern-day “Balfour Declaration” – the British Government statement that formally approved the creation of an Israeli homeland in 1917.

Ziad Thatha, the Hamas economic minister in the Palestinian Government, said: “BG Group is an embarrassment to the Palestinian people.

“When a company sells Palestinian gas to the Zionist occupation, it is similar to acts of theft the Israelis are practising against our land every day.”

The comments threaten to overshadow key negotiations BG Group hoped would lead to the development of the Gaza Marine gas field it discovered seven years ago. Talks over a 15-year contract are due to begin next week and the Israeli Foreign Ministry said it was keen to conclude a deal “as soon as possible”.

The Gaza Marine field is Pal-estine’s only sovereign natural resource and its development could generate £500 million for the Palestinian economy in royalties from BG Group. The gas would meet 10 per cent of Israel’s annual energy requirements. BG Group said that its priority was thrashing out a deal acceptable to the Israeli and Palestinian authorities. “We need a bilateral agreement for this project to get across the line,” a spokesman said.

However, Hamas controls a majority of the seats in the Palestinian Government. The more moderate Fatah Party reiterated yesterday that it wanted guarantees over how cash payments would be made before signing off any deal.

Mohammad Mustafa, the economic adviser to Mahmoud Abbas, the Palestinian President, said: “We hope that we will reach an understanding and remaining obstacles will be overcome.”

BG Group had been negotiating to pump gas from the field, which holds 1 trillion cubic feet of reserves, to Egypt before Tony Blair urged the company to give Israel a second chance last summer.

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