CAMPAIGNERS have criticised prosecutors for failing to pursue legal action against the UK's biggest bird conservation charity after it illegally chopped down thousands of trees.

The Crown Office said it was not in the public interest to prosecute the RSPB after it cut down 46 hectares of trees in Forsinard, Sutherland, to help create a wetland.

The work at the site, containing an estimated 40,000 trees, was carried out after their licence had expired, according to a lengthy investigation carried out by the Forestry Commission.

The RSPB faced a fine of twice the £15,636 value of the felled trees.

But the Crown Office has now decided not to prosecute the RSPB because to do so was "not in the public interest".

The decision was described as "disgraceful" by campaigners who have been fighting against the Forsinard Flows reserve, part of a five-year project meant to restore bogland habitat.

RSPB claims that as well as attracting a greater diversity of bird species, the bogland would be generally good for the environment.

But documents obtained under the Freedom of Information from the Forestry Commission show that the RSPB carried out felling without a licence. The two-year licence expired in December 2014 but contractors for the RSPB carried on working until March last year.

The Forestry Commission stated: "Due to the scale of the unauthorised felling we submitted a report to the procurator fiscal.

"They determine if taking a prosecution forward is in the public interest. In this case, the procurator fiscal decided prosecution was unwarranted."

A spokesman for Forsinard Says No, which claims the scheme will be an eyesore and attract too many visitors, said: "It's utterly disgraceful.

"It sets a precedent for anyone else to go and cut down trees. They can go into court and say: 'Well, the RSPB got away with it.'

"If you can't fine someone give them a sentence they won't like. Make them replant them. They got away with a slap on the wrist."

In December last year, farmer Kerry MacKenzie was fined £2,500 for chopping down 2,000 trees without a licence at Drumligair Farm, Newmachar.

Mr MacKenzie had claimed the trees were not worth anything, but was prosecuted on the basis that the Forestry Commission had valued them at around £11,000.

Speaking about the two cases, the Forsinard Says No spokesman said: "How can they claim it's not in the public interest when they can prosecute a farmer in Aberdeenshire for 2,000 trees?"

A Forestry Commission Scotland spokesman said: "In line with normal practice when there is an unauthorised felling of this scale and significance, a thorough report was produced and submitted to the procurator fiscal.

"It is for the procurator fiscal to decide whether or not to take forward any prosecution and in this case they decided not to do so.

"We have issued formal warning letters to the parties involved and met senior staff from both RSPB and Tilhill to ensure their procedures are revised to avoid such incidents in the future."

RSPB spokesman Dr Pete Mayhew said: "We welcome the decision by the procurator fiscal and look forward to moving ahead with our important peatland restoration work under a Forest Plan agreed with Forestry Commission Scotland.

"To ensure that there is no repetition of this unfortunate incident, we have undertaken a complete and thorough review of our operating procedures and strengthened them significantly so that we can focus on our work restoring the internationally important peatlands of the Flow Country.

"In addition our site management protocols have changed across the UK, with additional training now being undertaken at any sites where trees occur and require management."

A Crown Office spokesman said: "Following a full and careful consideration of the facts and circumstances of this case, including a number of mitigating circumstances, the procurator fiscal decided that there should be no criminal proceedings at this time.

"The Crown reserves the right to proceed in the future."