Environmental campaigners have warned there is a real risk that Scotland's climate plan will not deliver the reduction in emissions needed.

Friends of the Earth Scotland accused ministers of "flawed thinking" and "unjustified optimism" over the proposals - which are meant to help Scotland cut carbon emissions as part of plans to achieve net-zero by 2045.

The updated climate change plan, published in December, sets out what the Scottish Government insists are "bold actions" aimed at helping meet emissions reduction targets in the period to 2032.

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The document stresses this "will not be easy" and will require a "truly national endeavour with business, communities and individuals contributing fully" if targets are to be met.

The plan sets out for the distance travelled in car journeys to be cut by a fifth by 2030, and promises £180 million in funding for carbon capture and hydrogen technologies as well as £120 million towards zero-emission buses.

Environment Secretary Roseanna Cunningham is due to face questions from MSPs on the plan when Holyrood's Environment, Climate Change and Land Reform Committee meets on Tuesday.

But Friends of the Earth Scotland climate campaigner Jess Cowell said experts have already raised their concerns with MSPs.

Chris Stark, chief executive of the independent advisory body the UK Committee on Climate Change, said there is "nothing in the report" to indicate "whether the policies are sufficient".

Rachel Howell, a lecturer in sociology/sustainable development at the University of Edinburgh, told the committee there is "concern about the fact that the plans and policies for reducing emissions through other technologies and through behaviour change do not meet the necessary targets".

Ms Cowell told MSPs it is "increasingly difficult to scrutinise whether the policies are on track to hit targets".

With environment policies high on the political agenda ahead of Glasgow hosting the UN Cop26 summit later this year, Ms Cowell claimed: "There is a real risk that Scotland is setting out with a climate plan that cannot get us where we need to be.

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"We know the level of action we need to see by 2030 but we have no clear idea of whether the policies suggested in this document will add up to meet that target.

"The Government either doesn't know or won't say how much climate pollution will be stopped by their individual policies, instead offering vague estimates for entire sectors.

"As it stands, the update simply doesn't add up and it's hard to see how MSPs can properly assess it against its targets.

"Transport is our most polluting sector and while there is a welcome goal to cut total car miles driven on Scottish roads by 20%, there is a lack of a clear plan of how this will be achieved."

She also claimed the document "relies heavily on illusory promises of carbon capture, hydrogen from gas and hare-brained schemes to burn trees for energy".

Ms Cowell said there is "very real concern " that such technologies are "being used as a 'get out of jail free' card by the Government to make their figures add up, rather than doing the hard work of cutting emissions in the here and now".

She insisted: "With the UN climate talks coming to Glasgow next year, and the clock ticking on solving the climate crisis, Scotland needs a bold plan setting out steps to phase out fossil fuel extraction and use, while ensuring a just transition for workers and communities currently dependent on the industry."

A Scottish Government spokeswoman insisted however that the plan sets out a "credible path to meeting Scotland's targets"

She said: "In Scotland, we are proud to have the most ambitious legal framework for emissions reduction in the world.

"Our updated climate change plan has over 100 new policies to meet Scotland's emissions targets over the period to 2032 and help achieve a just transition to net zero by 2045. This is supported by a record £1.9 billion of capital funding in the Scottish Budget 2021-22.

"There is no doubt that these targets are immensely challenging and we are clear that delivering net zero will require action from Scottish society, businesses and the UK Government.

"However, we believe that the climate change plan - combined with action from other key actors - represents a credible path to meeting Scotland's targets.

"As we set out in the plan, the Scottish Government is prioritising the exploration and resolution of the issues associated with emerging technologies, backed by a £180 million Emerging Technologies Fund over the next five years.

"Carbon capture and storage is a proven technology and one that will be critical to net zero. There are over 20 installations operational worldwide and Scotland has the opportunity to pioneer their use to deliver major low and negative carbon infrastructure, as recommended by our statutory advisers, the Committee on Climate Change."