Bumblebees could be shrinking because of exposure to a widely used pesticide, a study suggests.

Experts fear smaller bees will be less effective at foraging for nectar and distributing pollen.

Scientists in the UK conducted laboratory tests which showed how a pyrethroid pesticide stunted the growth of worker bumblebee larvae, causing them to hatch out reduced in size.

Gemma Baron, a researchers from the University of London, said: "Larger bumblebees are more effective at foraging."

Pyrethroid pesticides are commonly used on flowering crops to prevent insect damage.