Scottish ministers are under mounting pressure to defy the Westminster government and back a European ban on toxic pesticides which are blamed for killing bees.

A powerful coalition of environmental groups is urging the Scottish Environment Secretary, Richard Lochhead, to support a move by the European Commission to restrict the use of nicotine-based nerve agents designed to kill insects that prevent crops from growing.

Lochhead has supported Westminster's rejection of a ban, stressing there are "gaps" in the science and concerns for farmers. But the Sunday Herald understands some of his senior officials now regard restrictions as inevitable.

Environmentalists point to more than 30 scientific studies, including some from Scottish universities, suggesting the pesticides are harming bees and other wildlife. Bees and other pollinating insects such as butterflies, moths and hoverflies are vital to the production of food, and are reckoned to be worth £43 million a year to the Scottish economy.

Chemicals called neonicotinoids are made by multi-national pesticide companies to paralyse insects. 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.

Now, a group of five environmental groups, led by the Scottish Wildlife Trust (SWT), has written to Lochhead asking him to back the proposed ban. It is due to be voted on in Brussels in two weeks, and the pesticides have already been taken off the shelves by eight UK retailers, including B&Q and Homebase.

Simon Milne, the SWT's chief executive, said it was "ridiculous" that Scotland and the UK were still saying the chemicals are safe.

"What the Government and industry should be doing is helping farmers move away from neonicotinoids to a more sustainable means of pest control which is also beneficial to wildlife," he argued.

The Royal Society for the Protection of Birds (RSPB), which has come out in favour of a ban, warned that the damage being done to pollinators was now apparent.

"Scotland is home to many bee species which are now scarce and declining across the UK," said RSPB Scotland's director, Stuart Housden. "The Scottish Government has a key role to play, not least in offering its full support for the European Commission's proposed recommendations restricting the use of neonicotinoids."

Other groups backing the ban are Buglife, Butterfly Conservation Scotland and Friends Of The Earth Scotland. They have also found an ally in the SNP MEP, Alyn Smith.

"I have no doubt the Scottish Government will be more interested in putting the health of bees and our environment first rather than allow the UK to decide for us," he told the Sunday Herald.

"To use the incomplete science as grounds for delay is just a shoddy lobbying tactic, and we owe it to Scotland's bees, and indeed ourselves, to act now."

However, the proposed ban was fiercely criticised by the Crop Protection Association, which represents the pesticide companies. It was "a disproportionate and alarmingly simplistic reaction to a complex problem," said the association's chief executive, Nick von Westenholz.

"The reasons there are declines in some pollinator populations, for instance bees, are complicated and not well understood, and include factors such as habitat loss, viruses and parasites."

He argued that pesticides are "vital tools" for farmers and removing them could have "serious consequences" for access to safe and affordable food.

The Scottish Government said its position was informed by scientific advisers. They had highlighted "concerns and gaps in the knowledge", said a spokesman.

"It is important to consider the potential risks to bees from neonicotinoids under field conditions. We have asked the advisory committee on pesticides for further urgent advice to help inform the Scottish Government's view on next steps."