The Conservatives have today formally committed themselves to annual targets on cutting carbon emissions - and said ministers might resign if they are not kept.
Leader David Cameron has pre-empted the publication of the government's climate change bill in the Queen's speech tomorrow by releasing details of his party's alternative proposals.
The Tory bill has the same goal as the government's - to cut carbon emissions by 60 per cent on 1990 levels by 2050. It also proposes an independent carbon commission, similar to the government's "carbon committee", to assess progress on this target.
But unlike the government, the party has today committed itself to year on year cuts to emissions, measured alongside annual "rolling targets" set and monitored by the carbon committee.
Tony Blair has previously dismissed annual targets as too inflexible and difficult to achieve - he argues that they must take account of external factors, such as weather, and says targets in five-year intervals are more appropriate.
The Conservatives accept some flexibility is needed, saying today that "we do not expect the government to meet the annual targets precisely each year", but instead proposed the rolling targets which could be increased or decreased.
"If there were genuine economic reasons why one year was especially difficult, the commission would take that into account and readjust the following year's targets to keep us on track for a cut of at least 60 per cent by 2050," a party spokesman said.
"However, if failure to meet carbon obligations arose - as over the past nine years - from government ineptitude or inertia, this would be exposed in a report which the secretary of state would be legally obliged to respond to."
The climate commission would be made up of scientists, economists, non-governmental organisations and representatives of industry, commerce and finance. Members would be nominated half by the environment secretary and half by the Royal Society.
As well as setting annual rolling targets, it would set framework goals for 2015, 2020, 2030 and 2040 to allow business and government to plan for long-term projects. It could impose targets on specific sectors if required.
"Climate change is one of the greatest challenges facing us today, and we can only tackle it if we realise that we all have a responsibility to act - individuals, businesses and government," David Cameron said.
"The government must deliver a proper climate change bill in the Queen's speech tomorrow - not a watered down version."