The Royal Bank of Scotland is facing mounting pressure over the climate-wrecking pollution it is accused of causing through its worldwide investments.

Campaigners from the international development agency Christian Aid last week met senior officials from the bank in Edinburgh and urged them to take responsibility for the coal, oil and gas plants that they help fund.

RBS recently shut a website it created that was dedicated to marketing the company as "the oil and gas bank". This followed an earlier report by pressure group Platform attacking the bank for going on a "destructive binge with potentially devastating consequences for the planet".

RBS is one of Scotland's most successful companies, a global brand recognised by millions because of its sponsorship of high-profile sporting events, such as the Six Nations rugby tournament. In March, it announced record profits of more than £9 billion.

But it has come under fire from environmentalists for its multi-billion-pound investments in industries which release the carbon said to cause global warming. The bank, however, says it can't be held responsible for the pollution caused by its customers.

The latest criticism comes from three Christian Aid supporters taking part in the UK's longest protest march to raise awareness of climate change. On Thursday, they visited RBS's offices in St Andrew Square to meet senior staff from the corporate responsibility team.

There, Mohammed Adow, who works for an organisation helping cattle herders in Kenya adapt to droughts, told them what he thought.

"The people I work with are suffering the impact of climate change already, but they are among those that emit the least amount of carbon," he said. "You can do so much more than they can to cut the carbon."

Just as supermarkets are now taking responsibility for their supply chains, RBS was urged to start talking about the carbon emissions of the industries it funds. Reducing the pollution caused directly by the bank's operations was just "the tip of the iceberg", according to Andrew Pendleton, Christian Aid's senior policy adviser on climate change.

"We are encouraging them, along with others in their industry, to disclose the full extent of the UK's global carbon footprint through lending and investments throughout the world," he said.

Christian Aid's Cut The Carbon march is an 11-week, 1000-mile trek across the UK which started in Northern Ireland on July 14 and is due to end in London on October 2. Marchers from around the world will travel though 70 towns and cities, and hope to involve more than 50,000 people in rallies and other events.

RBS said it was buying all its electricity from renewable sources in the UK and had invested £1.3bn in renewable energy. "We welcome the constructive discussion with Christian Aid and recognise the significant global threat posed by climate change," said an RBS spokeswoman.

"However, it is unreasonable to suggest that a bank should be held responsible for the carbon emissions of its customers. If this were the case, we would for example be held responsible for the emissions of every car and home we helped to finance."

In March, a report by the London-based environmental research group Platform, criticised RBS for assisting with more than £20bn worth of oil, gas and related projects since 2001. The bank subsequently took down its marketing website, theoilandgasbank.com. This was claimed as a "partial victory" by Platform.

RBS insisted oil and gas remained a very important part of its business. "We continue to produce the monthly RBS oil and gas index, and each year organise the annual conference for those involved in the UK oil and gas industry," said a company spokesman.