The bank has pledged to stop investing in companies which exploit fossil fuels or manufacture unnatural chemicals.

Trading on its principles and profits policy, the bank says it will also extend its ban on companies which carry out animal-testing.

It will refuse to deal both with companies who trade arms to oppressive regimes as well as companies who manufacture leg irons, water cannons and execution equipment.

The bank decided to tighten its rules after conducting a survey of its investors which showed that 87% supported an even greater ethical approach.