Scotland's £1 billion salmon farming industry has been accused of hiding "damning" information about its environmental dangers.

Salmon companies are refusing to send vital data to Scottish Government scientists, to avoid it being released under Freedom of Information law. On the few occasions they have had to forward information, it has been deleted by government officials.

The information is about one of the biggest problems plaguing salmon farmers – infestations of sea lice.

Evidence of infestations is used by environmentalists to criticise salmon farms. Critics of the industry say the Scottish Government has bowed to lobbying from the industry to keep details secret.

The law requires salmon farmers to regularly monitor the number of sea lice in their cages. They have previously sent the results to Scottish Government marine scientists in Aberdeen to help with research and treatment. The limited information available showed that levels of lice infestation in Scotland could rise to six times guideline limits.

In response to a Freedom of Information request last year, the Government's Marine Scotland Science said it had deleted data about three Marine Harvest farms because it had "no further use for it".

Marine Harvest stressed that it met legal requirements on lice reporting.