Peers have given their support to a government move to help health authorities persuade water companies to put fluoride in community drinking water.

Last night, the Lords voted 153 to 31, a majority of 122, on an amendment to the water bill which will indemnify water companies against any liabilities arising through fluoridation.

Flurodation, which is backed by many dentists and doctors, is seen as a cheap and effective way of combating poor oral health in deprived areas, particulalry in young children.

The bill will now go to the Commons in the autumn, where a free vote is expected on the issue, which has supporters and critics across the political divide.

Opponents say it infringes the civil liberties of those who do not want fluoridated water. There are also concerns about the safety of fluoridation, which has been linked with cancer and bone disease – although official studies have found no connection.

Water companies have had the power to fluoridate water supplies since 1985 but have not done so for fear of legal action from consumers opposed to it, apart from in Birmingham, where water has been fluoridated for over 40 years.

However, this decision by peers means that local health authorities will indemnify water companies if local people agree to fluoridate supplies, where it is necessary to improve dental public health.

Fluoridation will only take place if the water authority has been asked to do so by a strategic health authority, after consultation at local level has shown sufficient support for it.