In an interview broadcast on Wednesday, Hawatmeh said Ismail Haniya, the Palestinian prime minister, had given the document to Mahmoud Abbas, the Palestinian president.
The DFLP is a Damascus-based Palestinian group which advocates a tough line in confronting the Israeli occupation.
However, Hawatmeh's claim was challenged by Osama Hamdan, the Hamas representative in Lebanon. In an interview aired by Al Jazeera on Thursday, he denied that any meeting between Hamas and Israeli officials in London had taken place.
Abbas said recently that Ehud Olmert, the Israeli prime minister, had welcomed the idea of an unofficial line of communication between Palestinians and Israelis.
Arms for Abbas
In another development, Israeli officials said on Thursday that Egypt has sent a large shipment of weapons to the Gaza Strip to shore up Abbas.
They said the shipment of 2,000 automatic rifles and ammunition was approved by Israel and escorted through its territory by police on Wednesday. The officials were speaking on condition of anonymity because the delivery had not been officially confirmed by Israel, the Palestinians or Egypt.
The four lorries then crossed into the Gaza Strip through the Karni checkpoint, the officials said.
The weapons are meant to strengthen Palestinian security services affiliated with Abbas's Fatah, currently engaged in a violent struggle for power with Hamas, which controls the Palestinian parliament and cabinet.
According to the daily Haaretz, the details of the shipment were settled by Olmert and Abbas at their first official meeting, held in Jerusalem on Saturday night.
However, a spokesman for Abbas denied that any weapons had been transferred. "The talk about the president's security services receiving arms is unfounded and not true at all," Nabil Abu Rdainah said.
Miri Eisin, Olmert's spokeswoman, declined to comment, as did the Israeli defence ministry.
At the meeting on Saturday, Olmert also pledged $100m in withheld tax revenues to the Palestinian president, bypassing the Hamas-led government.
Israeli officials have said Washington has been instrumental in helping to organise a number of past shipments of guns and ammunition to Abbas's presidential guard from Egypt and Jordan.
The Bush administration is seeking congressional support to provide up to $100m to bolster the force and expand Abbas's control over strategic border crossings.