KLP, Norway’s main provider of municipal pensions, has added US oil giant Chevron back to its investment universe after a 13-year exclusion after the basis for the blacklisting was largely discredited.

The NOK641bn (€65.7bn) pension fund said a 2016 US court ruling meant that documents in an environmental case against Chevron – upon which the KLP exclusion was at least partly based – had been falsified, and witnesses and judicial officials had been bribed.

Anne Kvam, head of responsible investments at KLP, said: “We have been an active voice in calling for change at Chevron for years, despite the company’s exclusion.

“With Chevron’s inclusion in KLP and the KLP fund’s investments, we plan to continue our engagement with the company as an active owner.”

Chevron was banished from KLP’s investment universe in 2004 for links to serious environmental damage, relating to the company’s long-running legal battle over pollution in the Ecuadorian rainforest.

In 2000 Chevron bought Texaco, which had been involved in oil extraction in Ecuador years before. Local communities sued Texaco, and later Chevron, for restitution, and KLP’s exclusion had been based on documentation from this case.

But last year, a US appeals court ruling confirmed that lawyers for the communities had built their case on falsified documents and bribery of both witnesses and judicial officials in Ecuador.

As well as this, the pension fund said Chevron had made big improvements to its human rights policy and environmental management systems.

The Chevron decision was one of several changes the pension fund has made to its exclusion list. KLP said it had excluded two coal companies and one tobacco company from its investment universe.

Alongside Chevron, AGL Energy, Alstom and L-3 Technologies have also been brought back into its investment universe.

The changes were the result of a biannual review conducted by KLP with regard to the organisation’s Guidelines for Responsible Investment.

This month, KLP’s list of potential equity investments is to expand to around 6,000 companies, from 3,000, following new investments in a global small-cap index.