As part of the deal that formed the coalition, it was agreed to hold a referendum on the Alternative Vote, in which the Conservatives would campaign for First Past the Post and the Liberal Democrats for Alternative Vote. The referendum, held on 5 May 2011, resulted in First Past the Post being chosen over Alternative Vote by approximately two-thirds of voters. In May 2011, Clegg revealed plans to make the House of Lords a mainly elected chamber, limiting the number of peers to 300, 80% of whom would be elected with a third of that 80% being elected every 5 years by single transferable vote. In August 2012, Clegg announced that attempts to reform the House of Lords would be abandoned due to opposition for the proposals by backbench Conservative MPs. Claiming the coalition agreement had been broken, Clegg stated that Liberal Democrat MPs would no longer support changes to the House of Commons boundaries for the 2015 general election. The Lib Dem Secretary of State for Energy and Climate Change Chris Huhne in 2011 announced plans for halving UK carbon emissions by 2025 as part of the "Green Deal" which was in the 2010 Liberal Democrat manifesto.