As the government today published its climate change bill, the Liberal Democrats signalled that they would be pushing for the legislation to be significantly strengthened.

The bill, which will legally oblige successive governments to move towards a 60 per cent cut in carbon emissions by 2050, will start the process in the House of Lords with a vote expected within the next few weeks.

The government has signalled it would like the bill to gain Royal Assent by the spring in order for the first annual carbon budget to be set next September.

However, there are early signs are that opposition parties will table amendments to toughen up the legislation, which could delay the parliamentary process.

A spokesman for the Liberal Democrats said that the party supported the bill but wanted it to go further. "We will be pushing for an 80 per cent reduction [by 2050], we want other greenhouse gases like methane to be included in the legislation, and we want it to take aviation into account," he said. "We'd support the bill as being better than nothing, but we will be pushing hard for those amendments."

The government has said that the one of the first tasks of the new independent climate change committee, which will be formed under the legislation, will be to assess whether the targets should be increased to 80 per cent and whether aviation and shipping emissions should be included, but the Lib Dems maintain the scientific evidence means these changes should be made immediately.

The Lib Dems insisted it was unclear if the government would be able to force through the bill without any amendments. "The Tories have been talking about the environment so there is a chance their peers may join ours to push for amendments," said the party spokesman. "Equally, there are potential Labour rebels who feel strongly that the bill should be strengthened."

Separately, the government sought to downplay fears about the introduction of pay-as-you-throw waste management schemes, insisting that legislation included in the climate change bill means that just five local authorities will be granted permission to introduce pilot schemes.

It added that the schemes would have to be approved by Environment Secretary Hilary Benn and that local authorities would have to make the schemes revenue neutral by ultimately paying back to residents any money they collect from the pilots.