The ‘carbon credit card’, which would give every Briton a rationed carbon allowance, could be operational within five years, Miliband told the Guardian this week.

“It is a way of pricing carbon emissions into individual behaviour and it would recognise carbon thrift, as well as economic thrift,” Mr Miliband said.

He stressed that the card is in line with developing spending habits: “Twenty years ago, if I had said eight million people would have a Tesco loyalty card, no one would have believed me.”

As he presented a new study from Defra’s Centre for Sustainable Energy, Mr Miliband said: “Bold thinking is required because the world is a dangerous place.”

The card would regularly remind consumers of their impact on the environment, keeping environmental concerns at the forefront of public consciousness.

It emerged today that 2006 was the warmest year on record in the UK since 1659 – a statistic many analysts link to global warming.

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