LONDON (Reuters) – BP is to be evicted from the FTSE4Good ethical investment index due to its Gulf of Mexico oil spill, index compiler FTSE said on Friday, as BP said it would delay its third-quarter results due to the challenges of accounting for spill costs.

FTSE said BP would be excluded from FTSE4Good, which many managers of ethical funds use to screen companies before including them in their portfolios, from September 18.

“The Committee’s decision to remove BP followed consideration of the company’s response to the Gulf of Mexico oil spill, the environmental and social impact and its history of similar incidents,” FTSE said in a statement.

BP was earlier this year evicted from the DJ Sustainability Index. Ethical investors account for an increasing portion of share buyers and consequently the decisions could hit demand for BP shares in future.

Shares in BP, which declined immediate comment, closed down 0.9 percent at 411.65 pence, lagging a 0.4 percent drop in the STOXX Europe 600 Oil and Gas index.

BP said earlier it would delay the release of its third-quarter results by a week because of added accounting complexities related to the Gulf of Mexico oil spill, the worst in United States history.

The company said its quarterly figures, normally reported on the last Tuesday of the month after the end of a calendar quarter, would now be released on November 2, rather than October 26.

A spokesman said the decision came after it proved challenging to complete its previous quarterly numbers within the normal timeline and denied it was related to the discovery of any new liabilities.

BP on Wednesday produced an internal investigation into the explosion on the Deepwater Horizon drilling rig on April 20. The spokesman said the team compiling the report, which laid most of the blame on the companies BP hired to drill the well, had been supported by internal and external lawyers.

However, he said the lawyers had been “ring-fenced” from the rest of BP and denied their role was to frame the report — much criticized by the contractors and U.S. politicians — so as to help BP fend off lawsuits.

“Their role was to make sure everything in the report was legally watertight,” spokesman Andrew Gowers said.

(Editing by David Cowell and David Holmes)