“This is truly a birth of a movement,” declared Jeremy Ben-Ami, executive director of J Street, the dovish Israel lobby, at his group’s first ever national conference.

For Mr Ben-Ami, the three-day parley in Washington DC, which brought together 1,500 activists, was a success. It attracted attention from the media and the foreign policy community, gained a stamp of approval from the administration and many members of Congress, and overcame a boycott by the Israeli ambassador to Washington.

“A lot of people felt very alone, but now, knowing that we are here will empower them,” said Mr Ben-Ami.

The 18-month-old lobby got a boost by the Obama administration’s decision to send a high-level official. National Security Adviser James Jones promised the audience: “You can be sure that this administration will be represented in all future conferences of this organisation.”

Support also poured in from Congress, as 150 members joined the list of sponsors. However, 10 did withdraw, reportedly due to pressure from more hawkish pro-Israel activists. In addition, Israel’s embassy in Washington sent a low-level diplomat to monitor the talks, but Ambassador Michael Oren refused to attend.

Israeli opposition lawmakers at the event criticised Mr Oren for boycotting the group because of its critical approach to Netanyahu government policy.

“We also criticise the government,” said MK Shlomo Molla from Kadima.

The organisation attracted further criticism after it emerged that its student arm dropped the “pro-Israel” part of its “pro-Israel, pro-peace” slogan.

Californian Bob Filner told participants that he and other lawmakers had been intimidated by Jewish donors who threatened to pull funds from their political campaigns if they did not vote in line with the views of the mainstream pro-Israel lobby, Aipac. J Street aims to provide these lawmakers with alternative funds in the 2010 election cycle.