Beekeepers calling on the Government to vote in favour of a European ban on certain pesticides have been backed by Dame Vivienne Westwood and Katharine Hamnett.
The fashion designers joined campaigners in London to demonstrate against the use of pesticides and handed a petition at No 10 Downing Street.
Other groups involved in the protests included Friends of the Earth, Greenpeace, Pesticide Action Network UK, RSPB, and the Soil Association.
Beekeepers have gathered in Parliament Square to urge the Government to support an EU-wide ban on certain pesticides.
The demonstration comes ahead of a vote in Brussels on Monday which will decide whether Europe introduces a two-year moratorium on various neonicotinoid pesticides.
ITV News reporter Martin Stews reports:
Hundreds of campaigners, including fashion designer Vivienne Westwood, will make their voice heard today with a protest at the Department of the Environment.
They are urging Environment Secretary Owen Paterson not to block an EU proposal to suspend the use of certain pesticides.
A vote will take place in Brussels on Monday which will decide whether Europe agrees to introduce a two-year suspension.
Britain's bee population is under threat from the weather and the use of some pesticides, according to campaigners.
British bee farmers say numbers within some colonies have slumped by as much as 50% because of the long winter and last summer's wet weather.
The implications could be felt in homes across the country, not just on the price of honey but because and around a third of what we eat is pollinated.
Environment Minister Richard Benyon has spoken to Radio 4's Today Programme about the proposal by MPs to ban pesticides in order to save bees.
– Richard Benyon, Environment Minister
We want to make sure that we have the necessary evidence.
If the evidence backs up action that bans these chemicals then we will take that action.
We are saying to the European Commission, if they are going to do this, they need to carry out proper field-scale surveys to decide once and for all whether this would be the right step to take.
If we ban these, farmers will go back to older chemistries, such as pyrethroids, which could be much more damaging in the long run.
Environmental campaign group Friends of the Earth are urging the Government to ban bee-killing pesticides.
– Friends of the Earth senior nature campaigner Paul de Zylva is
MPs have hit the nail on the head. We need a clamp down on neonicotinoids and an end to secret pesticide testing.
This report proves strong cross-party support for halting bee decline. Over a quarter of all MPs back our demand for a Bee Action Plan to address all threats to bees.
Yet the UK Government is still failing to respond to this urgent issue. What else are they waiting for?
The renewed appeal follows today's report by the Environmental Audit Committee calling for precautionary action to protect insects such as bees, moths, butterflies and hoverflies
Industry body the Crop Protection Association have said there was no new evidence in the today's parliamentary Environmental Audit Committee report to justify banning the pesticides.
– CPA chief executive Nick von Westenholz
Calls for a suspension of neonicotinoid insecticides are a disproportionate reaction to a complex problem and there is no evidence that such a move will lead to any meaningful improvement in bee health.
The reasons that there are declines in some pollinator populations are complicated and not well understood and include factors such as habitat loss, viruses and parasites.
Similarly the call to withdraw the approval of neonicotinoids in gardens and amenity areas is unjustified and not supported by any evidence of harm from their proper use in these areas."
Meanwhile Defra's chief scientific advisor Professor Ian Boyd has said the issue surrounding pesticides and bees was finely balanced and that it would not be proportionate to ban the chemicals at the moment.
He said there was a trade-off between the costs of reduced crop pollination if populations of bees and other pollinators are affected and the costs of reduced yields or environmental problems associated with other pesticides that farmers would use instead.
The European Commission has called for the use of certain neonicotinoids to be restricted so they cannot be used on crops that are attractive to bees.
The UK however had urged the Commission to wait for the results of a Government-commissioned field study on bumblebees, which did not show conclusively that there was a major impact on the insects from the pesticides.
But today's parliamentary Environmental Audit Committee report concluded the research was "fundamentally flawed" and should not be used as a basis for inaction.
The MPs also said that when scientific evidence was incomplete or contradictory, the Environment Department (Defra) should take precautionary action rather than maintaining the status quo while waiting for further evidence.
The report also called for greater openness from pesticide companies, who use arguments of commercial sensitivity to keep data secret, so that their research into the environmental impacts of chemicals could be scrutinised.
And clearer targets were needed to reduce reliance on pesticides, it said.
Ministers have been accused of taking an "extraordinarily complacent approach" to protecting bees and insects from pesticides which are blamed for their numbers declining, MPs have said.
The parliamentary Environmental Audit Committee said the weight of evidence now warranted precautionary action to protect insects such as bees, moths, butterflies and hoverflies, many of which are suffering declines in numbers in the UK.
Concerns have been raised over possible damage to bees from exposure to neonicotinoids, with research suggesting immediate or long-term effects on bee colony survival and development, and disruption to foraging behaviour.
A moratorium on use of three neonicotinoid pesticides on crops such as oil seed rape which bees feed on should be introduced by the beginning of 2014, a report by the committee said.
And their use in private gardens and places such as golf courses should be banned immediately to create "an urban safe haven for bees".