Customers in Europe will pay an extra £1 per laptop and £3 per desktop. Dell will use the money to plant a tree that will absorb the amount of carbon generated in the production of the electricity used by the computer over its lifetime.
The expansion is part of a larger move by Dell to cut its carbon footprint and extend its environmental policy. The company is aiming to cut its carbon use by 15 per cent over the next five years.
Dell also said that it would begin recording greenhouse gas emissions in its manufacturing plants and use the data to help make manufacturing decisions.
The firm's IdeaStorm website will also begin gathering user input on how to make "the greenest PC on the planet".
"Our goal is simple and clear," said Dell co-founder and chief executive Michael Dell.
"We will take the lead in setting an environmental standard for our industry that will reflect our partnership with, and direct feedback from, our customers, suppliers and stakeholders, and we intend to maintain that leadership."
The environmental group praised Dell's recycling programme, but criticised its continued use of PVC and brominated flame retardants.
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