The Amnesty International and the Centre for Environment, Human Rights and Development (CEHRD) have disagreed with the claims by Shell Petroleum Development Company (SPDC) Nigeria Limited that sabotage was responsible for a seven-day-long oil spill in the Niger Delta region in June 2012.

The rights groups stated in a report that a recent investigation into the oil spill in the Bodo region was "a fiasco" and that there were inconsistencies in the sabotage claims made by the oil giant.

The 14-page report entitled: "Another Bodo oil spill, another flawed oil spill investigation in the Niger Delta," focused on the lack of transparency in the joint investigation carried out by Shell, members of the community and local authorities, as well as the failure of Shell to disclose any information on the condition or age of its pipelines in the region.

It was noted in the report that experts who had examined the pipes explained that there are strong indications that the leak was due to corrosion of the pipeline rather than sabotage as claimed by SPDC.

Amnesty and CEHRD had directed a United States firm, Accufacts, with years of experience in examining oil infrastructure, to examine photographs of the pipeline at the leak point.

The report noted that Accufacts found that damage to the pipeline was "apparently due to external corrosion".

The company pointed out a "layered loss of metal on the outside of the pipe around the "stick" from pipe wall loss (thinning) due to external corrosion," adding that: "It is a very familiar pattern that we have seen many times on other pipelines."

Commenting on the report, Director of Global Issues at Amnesty International, Audrey Gaughran, said: "The investigation process into oil spills in the Niger Delta is a fiasco. There is more investment in public relations messaging than in facing up to the fact that much of the oil infrastructure is old, poorly maintained and prone to leaks, some of them devastating in terms of their human rights impact.

He added: "No matter what evidence is presented to Shell about oil spills, they constantly hide behind the 'sabotage' excuse and dodge their responsibility for massive pollution which is due to their failure to properly maintain their infrastructure and make it safe, and to properly clean up oil spills."

Corroborating Gaughran's statement on the report, Director of Programmes at the CEHRD, Stevyn Obodoekwe, stated: "Shell has said locally that the spill looks like sabotage, and they completely ignore the evidence of corrosion. This has generated a lot of confusion and some anger in the community.

"We have seen the pipe and brought an expert to look at it, and it seems pretty clear it is corroded", he added.

The report also indicated that just one year ago, the United Nations Environment Programme (UNEP) issued a major report on the effects of oil pollution in the Ogoniland region of the Niger Delta but little had changed, as the latest oil spill at Bodo demonstrated.

It explained that among its findings, UNEP confirmed that Nigerian regulatory agencies were at the mercy of oil companies when it comes to conducting site inspections and UNEP also found that Shell had failed to adhere to its own standards in relation to maintaining its infrastructure.

Amnesty stated that corrosion of the pipelines and equipment failure have been responsible for the majority of spills in the Niger Delta and that in recent years sabotage, vandalism and theft of oil have also contributed to pollution but corrosion and equipment failure remain very serious problems which have never been addressed.

It added that: "Oil companies are responsible for ensuring that, as far as possible, their equipment is not vulnerable to tampering. However, Shell has not responded to a request for information on any measures it has taken to prevent sabotage and vandalism.

Since 2011, Shell has posted oil spill investigation data on its website. This move has been welcomed by Amnesty and CEHRD. But research by both organisations stated: "The process on the ground remains highly problematic, and there is a lack of independence and transparency in the investigations themselves."