The millions of people at risk of vitamin D deficiencies should have better access to supplements, according to new guidelines.

It's estimated 10 million people across England may be low on the vitamin, leaving them at risk of rickets and weak bones.

New guidance notes released by the National Institute for Health and Care Excellence (Nice) suggest local authorities consider providing free supplements to at-risk groups, and encourage pharmacies and supermarkets to stock the cheapest vitamin D supplements and promote them to at-risk groups.

A year's supply to an adult would cost around £6, according to Nice.

Another key recommendation is that the Department of Health work with manufacturers of vitamin D supplements to ensure that products contain the recommended daily amount of the vitamin.

Health professionals should not routinely test people's vitamin D status unless they have symptoms of deficiency, they are considered to be at particularly high risk of deficiency, or there is a clinical reason to do so, Nice says.

Nice Centre for Public Health director Mike Kelly said: "Around 10 million people in England may have low vitamin D status and so could be at risk of health problems - and they may not know it.

"People with darker skin are particularly at risk - during winter months nearly 75% of adults from Asian or African and Caribbean backgrounds may have low vitamin D levels.

"People who are over 65-years old are another group at risk of having low vitamin D levels, and so are also at risk of conditions like osteomalacia - soft bones.

"Nice recommends making low cost vitamin D supplements widely available to people at risk of deficiency."

The main natural source of vitamin D is through the action of sunlight on the skin.

But some individuals may need dietary supplements, especially through the colder months.

People with darker skin are at risk of having low vitamin D levels because their skin also doesn't produce vitamin D well following exposure to sunlight.

Other people at risk of vitamin D deficiency are pregnant women, children, older adults, and people who have limited sun exposure, such as those who cover their skin for cultural reasons.

The warning follows fears about the rising number of children developing rickets over the past few years.

A research paper by professor Simon Pearce, a vitamin D specialist, published in the British Medical Journal in 2010 put the number of children being treated for the condition at several hundred a year.

He also raised concerns that profound vitamin D deficiency could be linked to non-musculoskeletal conditions such as cancer and metabolic syndrome.

Janet Fyle, professional policy adviser at the Royal College of Midwives, said: "This is welcome guidance. The chief medical and nursing officers in the four UK countries reinforce the message to practitioners such as midwives to ensure that at risk groups - children, pregnant women and breastfeeding mothers take vitamin D supplementation and we support this.

"We would advise women to talk to their midwife or GP for advice on vitamin D supplementation. This is especially important if they fall within the 'at risk groups'."

A Department of Health spokesman said free supplements were already available to some at-risk individuals through the Government's Healthy Start voucher programme, which targets disadvantaged families.

But the department was working to roll out the availability of low-price supplements further, he said.

"Pregnant women, and families with young children, across the country should be able to benefit from Healthy Start vitamins such as vitamin D and we are making this happen," he said.