Emamectin is a pesticide designed to kill sea lice, tiny crustaceans that eat farmed salmon alive. But it also contaminates the seabed and kills larger crustaceans in the wild such as crab and lobsters.

Because lice are becoming resistant to the pesticide, salmon farmers have been using it in increasing amounts. At the same time, scientific studies have suggested that it could be causing widespread damage to marine wildlife.

It is no surprise, then, that scientists at the Scottish Environment Protection Agency (Sepa) privately recommended last year that emamectin should be phased out over two or three years. In 2015 they had come to the same conclusion about its predecessor, teflubenzuron, which was previously used to kill lice.

However, what we now know happened next is disturbing. In August 2016 Sepa told the fish farming industry it was planning to announce its intention to phase out emamectin.

This prompted a fierce flurry of behind-the-scenes lobbying. The industry and emamectin’s manufacturer, the US drug company Merck, told Sepa in no uncertain terms that this would be a bad idea.

As we report today, the industry also lobbied the environment secretary, Roseanna Cunningham. Her officials spoke to Sepa’s chief executive, Terry A’Hearn, and he decided to withdraw the planned announcement.

The Scottish Government insists that there was nothing untoward in what happened. Officials are right to inform ministers of the concerns of stakeholders, and it’s up to Sepa to regulate the marine environment.

Fair enough, some would say. But what’s concerning about the long email trails released under freedom of information law is the powerful, private presence of the industry. Their representatives are ubiquitous, and seem to be able to easily get the ear of ministers.

Of course salmon farming is one of Scotland’s most important industries, and provides much-needed employment in rural areas. Ministers have backed plans for the business to be doubled from £1.8 billion in 2016 to £3.6 billion by 2030.

But we need to be careful here. The natural environment has a major economic value too, and creel fishermen are very worried that fish farm pesticides are threatening their livelihoods.

It is important that we get the balance right. The accusation from environmentalists that wildlife is being sacrificed to help salmon farmers should not be dismissed out of hand.

That means that we need to take a closer look at the lobbying on emamectin. Were the industry allowed undue influence? Did Sepa bend too easily under pressure, and have ministers played the role they should have in protecting the wider public interest?

That’s why we think it’s now time for a parliamentary investigation. MSPs, over to you.