The environment secretary, Hilary Benn, today pledged that ministers would "reflect carefully" on a report by MPs and peers into the draft climate change bill.

The cross-party committee said today that judges ought to have the power to compel the government to set out measures to reduce carbon emissions if it failed to hit targets, and said that the failure to include aviation emissions in its carbon reduction targets reduced the targets' credibility.

Mr Benn said that the bill would be "the first national legislation of its kind in the world, helping us to cut emissions and showing the world that we're determined to make our contribution as part of a global agreement".

He called the bill's target of a 60% carbon reduction by 2050 was "ambitious by any standard and consistent with our leading position internationally", but said that the government would "keep this goal under review in the light of emerging scientific evidence and other developments".

The climate change bill is due to be introduced in the next parliament. It places a legal duty on the environment secretary to reduce carbon emissions by 60% by 2050, and sets out a series of milestones, including five yearly "carbon budgets" setting out projected carbon emissions.

But the joint committee of peers and MPs examining the bill - chaired by Lord Puttnam, the Labour peer and film producer - concluded that the enforcement mechanisms in the bill were unclear, and said that the 60% target "may not be adequate to prevent global temperatures rising above dangerous levels".

David Howarth, a Liberal Democrat member of the committee, called provisions in the bill that allowed for foreign carbon credits to be purchased to help meet UK targets "outrageous".

He said: "It puts off creating a low-carbon economy in the UK and relies on other countries making the necessary changes."

Martin Harper of the RSPB called for an 80% target and added: "The uncontrolled expansion of airports is a product of the government's myopic policy and has to stop. Ministers must include aviation emissions in legally binding greenhouse gas targets."

He called on the travel industry to "come to the table and talk about how they can cut their emissions".