Some of Scotland's best-known brands have been named and shamed by the ­Government's green watchdog for their poor performances on pollution, the Sunday Herald can reveal.

The Scottish Environment Protection Agency (Sepa) has fingered famous food company Baxters, beer giant Tennent Caledonian, and biscuit-maker McVitie's for breaching pollution limits. Whisky distilleries including Glenlivet, Macallan and Ardmore have also come under fire.

Other big operators condemned as poor are the Peel Group's Clydeport at Hunterston in North Ayrshire, which twice showered a local community with dust; the Wood Group's oil terminal at Nigg on the Cromarty Firth, which unleashed an "offensive odour"; and Borders General Hospital in Melrose, which twice breached air pollution limits.

A wood products factory at Cowie in Stirling, run by the giant Canadian corporation Norbord, was slated as "very poor" by Sepa because of pollution breaches. The same plant was "poor" in 2012 and 2010.

Sepa's latest "compliance assessments" rate the environmental performance of 349 industrial sites across Scotland in 2013 as either poor or very poor. The biggest offenders were 83 water suppliers, 82 waste industry sites and 45 fish farms.

There were also 32 private sewers, 29 public sewerage works, 10 distilleries and breweries, nine crematoria, six food plants and five open-cast coal mines assessed as poor (see table). Details of most polluters are posted online by Sepa, but it has kept water suppliers and sites handling radioactive substances secret "for reasons of national security".

Environmentalists say the revelations are "shocking" and slammed poor performers. But many firms have defended their records, saying they have made improvements.

"This is a sorry catalogue of incompetents, chancers and ­criminals, and Sepa needs to use the full force of the law to rapidly improve these poor figures," said Emilia Hanna, pollution campaigner at Friends Of The Earth Scotland.

"As usual the waste industry leads the table for being rubbish at looking after the environment - it is time they stopped getting away with it. And it's a disgrace that publicly owned Scottish Water is far from a shining example of good practice."

She added: "It is particularly disappointing that such a strongly iconic brand as Baxters is listed as a poor performer. Scotland's food and drink industry trades on the image of a clean environment but Baxters is letting the side down."

Family firm Baxters, based at Fochabers in Moray and best-known for soup, has been categorised as poor by Sepa for three years. In 2013. Sepa said it failed to comply with pollution limits, though compliance was expected to improve in 2014.

Baxters said it had invested £300,000 to improve its effluent treatment, and expected to spend more. "This has resulted in significant improvements and we have been complying with Sepa requirements for the past 12 months," said a company spokeswoman.

Among the 82 waste sites rated poor are landfills, transfer stations, processing plants and scrap metal dealers. Most are privately run but some belong to local authorities.

The Scottish Environmental Services Association (Sesa) represents the waste industry. It said more credit should be given to firms that perform well. "That the vast majority of Sesa member sites are in the upper compliance bands is a direct reflection of the effort and resources that are continually expended to secure compliance," said Sesa policy adviser Stephen Freeland.

The 29 public sewerage works rated as poor include plants in Glasgow, Lanarkshire, Ayrshire, Argyll, Stirling, Scottish Borders, Aberdeen and elsewhere. Sewers have overflowed, leaked and breached environmental limits.

Scottish Water, however, said 93% of its waste-water treatment works were classed as satisfactory, significantly better than 2012. "We are committed to delivering further improvements and in the forthcoming 2015-21 investment period will be investing a minimum of £480 million to protect and enhance our environment," said a company spokesman.

The 45 fish farms, most in the Highlands and Islands, failed Sepa's assessment for contaminating the seabed, overstocking salmon and breaking rules on use of chemicals. The Salmon & Trout Association in Scotland, which represents anglers, says this suggests Sepa is not acting robustly against offenders.

But Scott Landsburgh, chief executive of the Scottish Salmon Producers' Organisation, pointed out that over 80% of fish farms were rated good or excellent. "Fish are grown responsibly, respecting the environment while maintaining jobs and supporting rural economies," he said.

Six of the seven whisky distilleries classed as poor for breaching pollution limits are on Speyside.

The Scotch Whisky Association said it was "disappointed" when high standards weren't achieved.

The association's Rosemary Gallagher said: "The industry works closely with Sepa and other relevant organisations to ensure it goes above and beyond compliance requirements."

The Ardmore distillery near Huntly has been rated as poor two years running. It works with the Royal Society for the Protection of Birds (RSPB) to help eagles and is sponsoring the society's prestigious Nature of Scotland awards in Edinburgh this week.

Green MSP Alison Johnstone urged the RSPB to consider carefully its links with Ardmore. "As an influential membership organisation it will want to avoid any damage to its good reputation," she said.

Ardmore, owned by Japanese and US drinks giant Beam Suntory, said it had improved its performance since 2013. A £2m investment in a new effluent treatment plant "will ensure an environmentally compliant future for the site," said manager Alistair Longwell.

Sepa criticised Tennent Caledonian's Wellpark brewery in the east end of Glasgow for "major breaches" of maintenance conditions and a "gross breach" in emissions in 2013. The company insisted this was a "temporary position" due to a "one-off" leak of coolant.

The McVitie's biscuit plant at Tollcross in Glasgow was graded as poor for breaking discharge limits. Sepa said owner United Biscuits had done work that should improve matters. The firm declined to comment.

Clydeport accepted there had been two "isolated incidents" at Hunterston, but said that it had invested tens of thousands of pounds to minimise dust clouds.

The Wood Group's UK managing director, Dave Stewart, also blamed a "one-off isolated incident" for the bad smell at the Nigg oil terminal and promised to stop a recurrence. NHS Borders said power cuts had triggered pollution from the incinerator at Borders General Hospital but a new system should avoid future incidents. Steve Roebuck, a director at Norbord, said an issue with the water treatment plant in Cowie had been resolved by investing £250,000 in a new plant.

Sepa pointed out that it had assessed 5178 sites in 2013, 4478 of which were excellent, good or broadly compliant. "The level of compliance that we have seen is encouraging" said Sepa's ­executive director, Calum MacDonald. He added: "Appropriate enforcement action will be taken against operators who have consistently failed to meet the required standards."