Kumi Naidoo, the global head of Greenpeace, is losing patience with the ability of companies and financial institutions to move away from their destructive behaviour.

While he recognises that there are a few progressive business leaders who share his concerns, Naidoo says he is planning to step up his campaign to hold them to account.

The sector most clearly in his sights is finance, given its power to support the transition to a green economy or continue to fund the destructive fossil-fuel industry.

He accepts that the NGO community made a mistake by not targeting the sector earlier and this was because it shied away from the complexity of the financial markets. But no more.

For the past two years Greenpeace has been working to understand not only how the financial markets really work, but also the leverage points where it can be most effective in seeking change.

Speaking on the day when he told the Guardian that Greenpeace is moving to a war footing as a result of the failure of negotiators at Rio+20 to agree clear policies and targets, he said: "We did not understand the financial markets but you have to appreciate that they are made not to be understandable. I know even financial journalists struggle to fully get it because its durability is based on opaqueness and a lack of transparency.

"We have been investing a lot of effort over the past couple of years to understand the industry and where the leverage points are and I think we are close to this point and finance institutions should be put on notice that not only Greenpeace but others are going to be putting them under much greater scrutiny.

"Our aim is to get all banks to say we won't make loans to oil, coal, gas and deforestation-related activity. We want to shut off the flow of capital. The time is right because the banks are at their most vulnerable in terms of public legitimacy."

It's not just the banks that will be targeted but also the pension funds. Naidoo, who was an anti-apartheid activist from the age of 15 and arrested and charged for violating state of emergency regulations in 1986, said it was simply unacceptable that pension funds invested money in activities that the owners of the money would not find acceptable.

While he supports the work of Fair Pensions in the UK, he warned City firms that Greenpeace intends to take campaigning "to a completely different scale."

Beyond the finance sector, Greenpeace plans to increasingly instigate consumer boycotts of consumer-facing brands but said the real environmental criminals were the companies largely invisible to ordinary people, such as commodity traders.

A primary target is likely to be Shell, despite the fact that the oil giant recently sought injunctions against each Greenpeace office around the world.

"We will be intensifying the pressure and if need be we will go after the brands and actually severely undermine them," he says. "With Shell we are taking the risk and we know they can come after us as they have an injunction against us but we will go after them."

While he admires corporate leaders who are prepared to stick their necks out, he says that even they are constrained by the system in which they operate.

While he believes the only answer to the current crisis is to have a complete redefinition of the notion of growth, he recognises that business cannot fundamentally change its ways in the absence of governments changing the rules of the game.

He said: "We have been engaging aggressively with business trying to provide them with technical expertise and to give them guidance on how to act more in more environmental ways.

"Big business is starting to understand that they have as much to lose if the whole planet goes to pot, but we have to ensure business leaders are not strangulated by the tyranny of quarterly reporting cycles which is what the situation is right now.

"I met with the senior management team at Macro, which is the third largest retailer in the US, and I said Greenpeace is more committed to its business in the long term than they are.

"They were shocked and asked what I meant. I told them that fish forms part of their product line and if they continue sourcing fish from unsustainable sources then the end result will be to kill their product line. We are not against palm oil or fishing but against what is unsustainable."

Naidoo says there is still a great deal companies can do in the absence of government intervention; stop selling products people do not need, break the conspiracy with marketing companies to promote wasteful consumption, and look at their entire supply chains, including the energy they buy, the materials they use and the way workers are treated.

He also called for companies to get more involved in political advocacy. When asked if he would campaign alongside companies he said: "That is not outside the realms of possibility but the reality is that at the moment it happens less directly."

He pointed out, however, that when Greenpeace unveils its campaign later this week against Arctic oil exploration, two senior business leaders will be in attendance and several other are expected to sign their declaration.

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