The Scottish Government has come under fire for failing to ban pesticides blamed for poisoning bees and threatening Scotland's £100 million soft fruit industry.

The Environment Minister, Richard Lochhead MSP, has refused to outlaw the use of nicotine-based toxic chemicals used by farmers to kill insects that damage crops. This is despite mounting evidence that the toxins harm bees, which pollinate strawberries, raspberries and other soft fruits.

The 30,000-member Scottish Wildlife Trust is now launching a campaign to ban the pesticides, known as neonicotinoids. Trust officials met with Lochhead earlier this month, but came away frustrated by his failure to act.

"We are extremely disappointed with the Scottish Government's response to our call for a moratorium on neonicotinoids," said the trust's head of policy, Dr Maggie Keegan. "We urge the Government to adopt the precautionary principle and ban these chemicals until there is convincing scientific evidence that pollinator populations are not significantly harmed."

The trust warned that delaying a ban could have a devastating impact on pollination, which is economically vital, particularly to the soft fruit growing industry. Neonicotinoids are already banned or restricted in France, Germany and Italy, but not in the UK.

The chemicals are made by multi-national pesticide companies to paralyse insects by attacking their nervous systems. With sales of more than £1 billion a year they are the world's most widely used insecticide, and are applied to 10% of Scotland's crop-growing land, mostly to protect oil seed rape.

A series of scientific studies in recent years have linked neonicotinoids to the "colony collapse disorder" that has decimated bee populations around the globe. The chemicals have been shown to impair the homing and foraging abilities of both honeybees and bumblebees.

Keegan criticised Lochhead for failing to question the insistence by the Department for Environment, Food and Rural Affairs (Defra) in London that the pesticides were safe. "The Scottish Government has dismissed a growing body of evidence out of hand, relying on Defra's stance and accepting it as their own without question," she told the Sunday Herald.

"Yet we have scientists in Scotland who have conducted research showing the harm of these chemicals to bees, and to the best of our knowledge officials have not asked them about their research."

Keegan pointed out that Defra's refusal to ban neonicotinoids was being challenged in Westminster by the House of Commons Environmental Audit Committee. MPs have accused pesticide regulators of "turning a blind eye" to the dangers for bees.

"We believe it is a very sorry state of affairs when we are continuing to use something that is harmful to wildlife because no alternatives are readily available," she argued. "A ban would put pressure on the pesticides industry to manufacture an alternative that is not harmful to the environment."

The Scottish Wildlife Trust was backed by one of the leading researchers to have raised concerns about the pesticides, Professor Dave Goulson from the University of Stirling. "I agree that neonicotinoids should be withdrawn pending further investigations," he said.

"The evidence for impacts on bees, particularly wild bumble- bees, keeps mounting, and to continue using them does risk further harming bee populations, particularly in the light of recent evidence that they accumulate in the environment."

Scottish ministers defended their refusal to ban the pesticides by pointing out they were following the advice of UK Government bodies. "We are watching this issue very carefully," said a Scottish Government spokesman.

"Pesticides are only approved if they are authorised after a rigorous assessment. This assessment includes assessing potential risks to wildlife, including foraging bees."

He added: "The issue is being kept under review, and we expect the next round of scientific advice early in 2013, which the Scottish Government will of course take very seriously."

The need for a ban was also disputed by the pesticide industry, which blamed other factors for the decline of bees.

"The causes of poor bee health are multifaceted and include parasites such as the Varroa mite and Nosema, viruses and diseases, a lack of genetic diversity, a lack of suitable forage and nesting habitats, and stress-induced impacts," stated a spokeswoman for the Crop Protection Association.

Research must be based on pesticide levels that were representative of real situations, she said.

"Our industry is actively involved in working with all stakeholders, including beekeepers, farmers and the scientific community, to gain a better understanding of the science surrounding bee health."