Battle for the green vote hots up with Brown turning fire on Cameron's 'spin'

Gordon Brown has called into question David Cameron's green credentials as Britain's two would-be prime ministers prepare to go head-to-head on the environment.

While the Tory leader visits an Arctic glacier today to see the dramatic effects of global warming, the Chancellor will pledge further domestic and global action to combat climate change in a keynote speech to the United Nations in New York.

In a pre-emptive strike last night, Mr Brown suggested that Mr Cameron's conversion to the green cause was based on spin rather than substance. He told the BBC: "The big issue on the environment is whether politicians can move beyond words to talking about the substantive policies necessary."

Challenging Mr Cameron to support the Government's climate change levy on industry, Mr Brown said: "If you want to support environmental policies you've got to support them in deeds. This means difficult decisions that require leadership. You are going to be judged in the end on the deeds, on what you have been able to do and how you can bring the rest of the world round to the policies that need to be followed." Brown aides contrasted the Chancellor's appearance on the world stage with Mr Cameron's visit to "a glacier" and the Tories' call for people to change their behaviour to help the environment with Mr Brown's plan for worldwide action.

In New York today, Mr Brown will argue that a new global consensus on climate change is both essential and possible. He will warn that "failure to act on the environment will put at risk future economic activity and growth" and claim that "far from being at odds with each other, our economic and environmental ambitions reinforce each other".

He will say: "Environmental sustainability is not an option, it is a necessity. For economies to flourish, for global poverty to be banished, for the well-being of the world's people to be enhanced - we have a compelling... duty of stewardship to take care of the natural environment and resources on which our economic activity and social fabric depends."

In a sideswipe at the Bush administration, Mr Brown will say the question is not whether climate change is happening but how fast it is happening.

He will say: "We will need a comprehensive global response. We will need the co-operation of all countries with significant energy needs and emission levels if - to the benefit of us all - we are going to tackle the global challenge of climate change comprehensively and cost effectively. Working apart we will fail."

Mr Brown will highlight the need to extend measures such as carbon emissions trading schemes for businesses across the European Union and will urge the World Bank to back a new $20bn-a-year (£11.2bn) plan to finance cleaner and more efficient energy for rapidly growing countries.

Four thousand miles away in Norway, Mr Cameron will visit a glacier that has lost up to half its mass in the past century. He will meet scientists on the archipelago of Svalbard to discuss dramatic falls in the Arctic sea level in the past 30 years.

Tomorrow the Tory leader will make a speech on climate change and visit the Nydalen business park in Oslo, where the local authority has ensured it is heated entirely by the use of geothermal boreholes in the ground.

Mr Cameron said last night: "Geothermal power is one of many emerging sustainable technologies which other countries are adopting and developing. Decentralised energy could play a much greater role in energy provision in the UK."