Concerns over a firm's environmental credentials dominate the agenda of ethical investors, according to a major new survey from Standard Life Investments.

The company surveyed 3,000 investors in its ethical funds and found that eight of their top 10 concerns related to the environment, with only two slots reserved for concerns over human rights policies and working conditions.

Fears that companies are involved in tropical rainforest deforestation or use of unsustainable timber topped the list, with firms operating in countries with poor human rights records without a clear policy on the issue ranked as the second biggest concern.

The rest of the list was dominated by environmental issues, with ethical investors expressing their desire to avoid firms with poor pollution and chemical manufacture records and back firms that have good environmental management systems, interest in renewable energy and strong policies for promoting biodiversity.

Julie McDowell, head of sustainable and responsible investment (SRI) at Standard Life Investments, said that the focus on environmental concerns was to be expected, given growing awareness of the threat posed by climate change.

The survey also found that a company's climate change policy is the top concern for 17 per cent of ethical investors, with 53 per cent of respondents viewing it as one of their top three concerns. Meanwhile, 30 per cent said they would exclude airline stocks from their investments altogether.

McDowell said that the committee that determines the criteria Standard Life uses to select ethical investments would assess how the results could shape the company's investment selection processes, paying particular attention to the increased investor concerns surrounding climate change and aviation.

For companies looking to attract increasingly influential ethical investors, McDowell said the survey's findings highlighted the importance of having string policies for reducing carbon emissions and ensuring supply chains follow environmental and human rights best practices.

"The survey found 91 per cent of respondents would invest in firms with a high impact on climate change so long as they are doing their best to limit those impacts," she said. "The indications are that ethical investors are more interested in helping companies improve than in avoiding them completely."