Australia's top 200 companies face a total annual cost of up to $2.8 billion under the federal government's still to be finalised Carbon Pollution Reduction Scheme (CPRS), a research and advisory firm says.

RepuTex has analysed the carbon footprint of all firms that make up the benchmark S&P/ASX200 stock exchange index to determine which ones are directly liable under the CPRS, and exposed to indirect supply chain and electricity cost increases.

"Between two per cent to three per cent of market value could be lost from the S&P/ASX200 if companies do not take action to mitigate their carbon exposure," the Melbourne-based RepuTex warned in a statement on Tuesday.

Under the proposed CPRS, to be phased in from July 2011, the medium-term target is to reduce Australia's greenhouse gas emissions by between five per cent and 15 per cent below 2000 levels by the end of 2020.

The target could be lifted to 25 per cent as part of a package of measures announced by the federal government last month.

RepuTex says the total liability for S&P/ASX200 companies in 2011 will be about $544 million, with the highest burden on the utilities, energy, industrials, materials and consumer staples sectors.

After 2012, annual carbon liabilities for these companies will rise to between $3.2 billion under the five per cent target and $4.9 billion under the 25 per cent goal.

But 42 per cent of this cost is expected to be passed on to consumers and supply chain partners, resulting in a net cost to S&P/ASX200 firms of $1.8 billion under the five per cent target and $2.76 billion under the 25 per cent objective.

RepuTex noted the S&P/ASX200 companies provided little information on their carbon footprints to the market, so the reliability of the data for analytical purposes was questionable.

"Only 31 per cent of S&P/ASX200 companies disclose their carbon footprint," RepuTex said.

"Disclosure in highly exposed sectors such as materials, energy and utilities is as low as 10 and 15 per cent."

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