This policy position was published by Sustrans in February 2015.
Helmet wearing isn't a legal requirement in the UK, and the evidence is inconclusive as to whether it makes cycling safer.
What does make cycling safe is changing the layout of roads, streets and public space to make them safer for people to get about by bike.
In the Netherlands, for example, it is the way that space is designed that leads to people of all ages and abilities getting about by bike safely rather than helmet wearing.
In places where a helmet law has been passed, cycling numbers have actually decreased.
Indeed, given the current concerns about obesity and the many thousands of deaths related to physical inactivity, making it compulsory for people to wear helmets provides a deterrent to people wanting to cycle, and also sends the message that travel by bike is dangerous rather than easy and a great way to get around.