The Australian Government has been accused of bullying and short-changing East Timor.
Australia and East Timor have formally signed a treaty to share the revenue from the main oil and gas field in the Timor Sea, ending a two-year dispute.
The deal means each country will take half the revenue from the Greater Sunrise Field and any negotiations on maritime boundaries will be postponed for up to 50 years.
Prime Minister John Howard says the agreement will further strengthen relations between the two countries.
But Timor Sea Justice Campaign spokesman Tom Clarke says East Timor would have had rights to all of the resources if Australia respected conventional maritime boundaries.
"You've got the poorest country in Asia, one of the smallest countries in the world, and then you have Australia, which is a very wealthy country," he said.
"It's a bit like if someone was dying of thirst in the desert, you're not going to be in a good position to negotiate the price of a glass of water and I think that's the case here.
"They're sharing the Greater Sunrise gas field 50/50 and the Australian Government has basically bullied the poorest country in Asia into postponing its claim to sovereignty of the area.
"So a permanent maritime boundary will not be established under this deal – they're basically leaving that issue for future generations to negotiate."
The Timor Sea Justice Campaign has also said the postponed decision on maritime boundaries means East Timor will not be able to gain control of the territory.
But Mr Howard says the foreign ministers from both countries have benefited both countries in signing the agreement.
"The treaty-signing is a very important event in relations between Australia and East Timor," he said.
"I congratulate Mr Downer and Dr Ramos Horta for the patient, careful, [and] on occasion laborious work that was involved in bringing out a fair and just outcome.
"It provides, over the years ahead, a very important addition to the revenue stream coming to a tiny independent country.
"There's great affection in Australia for East Timor, there's great sympathy for the people of East Timor, there is a great desire on the part of the people of Australia that the people of East Timor have a strong secure future."