Special bricks could attract mites or encourage spread of disease if not cleaned properly, say some experts
An initiative in Brighton aimed at helping protect the bee population could do more harm than good, scientists have warned.
The council in Brighton has passed a planning condition that means any new building more than five metres high will have to include swift boxes and special bricks with holes known as bee bricks. They will provide nesting and hibernating space for solitary bees.
There are about 270 species of bee in Britain, just under 250 of which are solitary bees that live alone, although often nest close to one another.
Solitary bees in Britain are highly diverse, and so are their nesting habits. Most British species nest in the ground, excavating their own nest.
The honeybee is probably the best-known bee. They live socially and are led by a queen and serviced by male drones and female worker bees.
The bee population is thought to have declined in the UK since the 1970s. For example, the number of managed honeybee hives in England dropped by 50% between 1985 and 2005, and 67% of common widespread moth species have declined since the 1970s.
Since 1900, the UK has lost 13 species of bee, and a further 35 are considered under threat of extinction.
The decline in population is thought to be because of changes in land use, which has led to habitat loss. Other issues affecting bees include disease, pesticides, pollution and climate change.
One of the best ways of helping bees is thought to be by planting flowers rich in nectar.