The Indonesian government has formally requested Australia's cooperation in resolving a dispute over an oil spill that it says had a devastating impact on coastal communities.

In August 2009 the wellhead blew at the Montara platform in Australian waters and crude oil spewed out into the Timor Sea for 74 days.

Some estimates put the rate of leakage at 500,000 litres per day as the company worked to cap the well and sprayed chemicals on the ocean to disperse the oil.

The company responsible, PTTEP Australasia, is a Perth-based subsidiary of a Thai-owned company.

Indonesia has little or no power over the company as it was operating in Australian waters, and Australia previously said it had not received a request from Indonesia for help.

Now, five years after the disaster, the ABC's Lateline program has obtained a letter sent by the Indonesian environment ministry last week formally requesting cooperation from Australia.

"The devastating impact of the Montara incident has been strongly felt by the people living in the coastal area[s] … as oil from the Montara well spilled over and crossed into [the] Indonesian EEZ (economic exclusive zone)," the letter said.

It asked for Australia's cooperation, also saying negotiations with the company had not been successful.

"After the incident, efforts to obtain appropriate compensation from the responsible parties in the incident for the economic social and environmental impacts has proven to be a difficult and complicated matter… " the letter said.

It asked Australia to "encourage" PTTEP Australasia to resolve the matter.

A statement from PTTEP Australasia said:

"Permission was not received from the Indonesian government to conduct research within Indonesian waters. "Modelling shows no oil reached the Australian or Indonesian mainland and that 98 per cent of oil remained within Australian waters, most of which was within 23 kilometres of the wellhead."

But some experts disagree with that assessment.

California-based expert Dr Bob Spies advised on the clean-up after the Exxon Valdez and Gulf of Mexico spills.

"I'd estimate about 20 per cent went into Indonesian waters," Dr Spies said, looking at satellite imagery of the Montara oil spill.

Seaweed farmers in coastal areas of Indonesia were among those affected by the Montara oil spill. ( ABC News )

He also travelled to Kupang in West Timor and said the anecdotal evidence suggested the communities there were affected.

"Without a good study, we don't know how it stacks up against the Gulf of Mexico BP spill or the Gulf of Alaska Exxon Valdez spill," Dr Spies said.

Even though the amount of oil that haemorrhaged from the Montara wellhead was far less than those spills, Dr Spies said smaller spills could have bigger impacts, depending on the marine environment they affected.

"It could've had a big impact. It could've been similar to the Gulf of Mexico. In fact, the environments are not dissimilar," he said.

Dr Spies backed the community's argument for an independent scientific study.

Dead fish, dolphins and a whale witnessed by Australian expert

Australian Fisheries Management expert Richard Mounsey was in the area at the time of the spill, working as a consultant to the East Timor government.

He said he witnessed the effects of the oil spill first hand, with the water turning murky from a combination of oil and the chemical dispersants used to break the oil slick down.

"I was in a small enclave [belonging to East Timor] that's in West Timor, Indonesia. I used to go the beach on my small boat every morning," Mr Mounsey said.

"And I noticed in early September 2009, when I jumped in the water to have a snorkel and to look around at the fish and the corals, it was like jumping into foggy water, it was all milky.

"I hadn't seen that and I'd been in East Timor off and on for the last eight years."

He said he did not realise there had been an oil spill.

Anecdotal evidence suggests in West Timor have been affected by the Montara oil spill. ( ABC News: George Roberts )

"At the time I had no idea, I thought, you know, 'what's going on?'," he said.

"Then I moved the boat … three or four kilometres somewhere else and the water was the same, and then I went in to the fishermen, they said there [were] small fish dying along the beaches.

"But everywhere I jumped in the water, there was nothing, it was like a dessert, except for this milky sort of fog.

"I found out later after going to Indonesia and finding out what was going on, and it appears that it was a dispersant that was mixed with the oil … so it was this film that had spread."

Mr Mounsey said a pod of dolphins native to the area disappeared and some turned up dead on the beach as well as a blue whale.

"I don't think Indonesia's to blame or Australia's to blame, but the company's playing them against each other which gives them a way out," he said.

The Australian Lawyers Alliance sent a delegation to Kupang in West Timor last year in order to investigate the claims of ongoing problems.

The group found anecdotal evidence of medical conditions such as rashes, cysts and other complaints that allegedly began occurring after the spill.

"However, we believe that claims that no oil reached the Indonesian coastline no longer have credibility in the face of the evidence in East Nusa Tenggara, Indonesia," the Alliance said.

"East Nusa Tenggara is one of the poorest provinces in Indonesia and is ranked as one of the top five priority provinces by the Australian aid program."

The Alliance also referenced a report by Dr Mukhtasor of Indonesia's Centre for Energy and Environmental Studies, which found more than $1.5 billion is being lost across the region every year since the spill.

Local communities still claim effects

Marlens Lauwe's crops are now contaminated with a strange white substance. ( ABC News: George Roberts )

Lateline travelled to West Timor earlier this month to interview people living along the coast.

A 54-year-old seaweed farmer, Marlens Lauwe, has been tending his crops in the shallow waters of Tablolong, West Timor, since the start of the century.

"Before 2009, around 2007-08, our income [was] increasing. Each time we harvested we [could] get four to five tonnes and the price at that time ranged between 15,000 to 20,000 per kilogram," Mr Lauwe said.

He said after the oil spill the growth of the seaweed was stunted and a white substance appeared on the crops, particularly affecting the most prized variety known as "green gold".

The bright green seaweed is valued for an extract that is used in cosmetics and pharmaceuticals.

Seaweed crops have started to recover, but their growth is stunted and is contaminated with a strange white substance.

"We still can earn money but not much, the money is small. We only can get 500,000 to 1 million rupiahs per month," Mr Lauwe said.

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His wife, Rin Lauwe, breaks down in tears explaining how it has become hard to feed the family.

"Not to mention the need for education, from elementary school, high school to the college… my heart is broken … [it's] so painful," she said.

"It is not enough," Mr Lauwe said, showing an itchy rash that he says began to appear after 2009.

Further along the West Timor coast at Lifuleo, Arbet Saketu said he and other farmers and fishermen get irritated skin.

"The itchiness which we experience [is] around April when the east wind rises," Mr Saketu said, pointing in the direction of the Montara oil field.

"From this direction," he said. "That's in April when fisherman and seaweed farmers here experience that."

West Timor businessman Ferdi Tanoni has been appointed by the local government to represent the coastal communities and has spent five years arguing for a scientific study into the impact on Indonesian communities.

"We have to be fair. The oil company has to be fair," Mr Tanoni said.

"If [they] find nothing, they pay nothing, but if they find something they have to be responsible, either the oil company or together with the Australian Government."

Mr Tanoni estimates 100,000 people have been affected across the surrounding islands.

He is travelling to Canberra, with the backing of the Indonesian government, in order to take up the matter directly with the Australian Government and argue the case to make the company pay for an independent study.

"If there is nothing happening out here, why are they afraid to conduct the study? This is only a simple question," he said.

Australia confirms another request for help

Lateline asked the Australian Government for a response to the letter from the Indonesian environment ministry.

A spokesman for the Department of Foreign Affairs and Trade confirmed another request for help from Indonesia, saying it: "… is aware that the Indonesian ministry of transport wrote to the Australian Maritime Safety Authority (AMSA) on September 19, 2014 seeking information and assistance in relation to the settlement of claims arising from the Montara oil spill of 2009.

"The department will be discussing the issues raised in the letter with AMSA and other relevant Australian agencies.

"Scientific studies were conducted in Australian territory following the oil spill.

"We understand that remote sensing indicated that oil did not reach the Indonesian coastline.

"These studies have been shared with Indonesia by the department."

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