Water bosses have admitted fluoride might have to be added to the tap water of people who have never been asked their opinion on the controversial process if the scheme is to work, the Daily Echo can reveal.

Campaigners believe the Hampshire project could become illegal if authorities attempt to introduce fluoridated water in areas not included in the original consultation on the plans.

Southern Water has said it is still trying to work out where the affected water would actually be delivered to under the proposal to add the chemical to drinking water across two-thirds of Southampton and parts of Eastleigh, Totton, Netley and Rownhams.

But the utility firm said it can make no promises areas outside of the initial proposals would not be included in the network receiving fluoridated supplies because of the way water is distributed.

Opponents of fluoride say they believe it would make the scheme illegal and are now assessing their legal options.

Hampshire Against fluoridation chairman Stephen Peckham said he also believes Southern Water’s admission it is still assessing how and where the scheme would work, as well as how much it will cost, wrecks South Central Strategic Health Auth-ority’s claims fluoridation is a cost-effective way of reducing tooth decay in children.

This weekend marks the third anniversary of the SHA board’s controversial unanimous decision to approve fluoride in Hampshire despite 72 per cent of respondents to a public consultation saying they opposed the plans.

Mr Peckham said: “We are three years on and we don’t know what the scheme will involve or how much it will cost. It’s absurd. Nothing’s in place, no contracts have been signed.

“It just shows it hasn’t been properly thought through.

“If they’re still trying to work out its feasibility how can they have already approved a scheme as feasible, it seems a little late to be looking into it now.”

Southern Water was first asked by the SHA to begin work on introducing fluoridation after the board’s decision in February 2009 based on a scheme identified in an initial feasibility study in 2008.

That project was put on hold a few months later when a legal challenge was lodged against the SHA’s actions.

But when a High Court judge last year rejected that judicial review the water firm was once again asked to re-start its work.

Senior customer relations adviser Sharon Collins said the company is now carrying out “a further feasibility study which will deal with the specific investment and operational requirements for this scheme”.

But she admitted it is not known whether it will actually be possible to run the project as thought in 2008, which was identified as schemes one and seven.

She said: “This study will take into account a review of the distribution system within the area, having regard to current arrangements and any future changes.

“Accordingly, at this time, I am unable to give my categorical assurance that only the post code areas defined in schemes one to seven of the original ‘high level’ feasibility study will receive a fluoridated water supply.”

Mr Peckham said that raises the prospect of the scheme potentially becoming illegal by falling foul of the Water Act, which says a water company must accept a request from health chiefs to fluoridate supplies “within the area specified in the arrangements”.

And he said this isn’t the first time it has been suggested fluoridation could affect areas not in the original plans.

Mr Peckham said: “Caroline Nokes was told at one point that Romsey would end up with fluoridated water at some point, but that it wouldn’t be a problem.

“But it will become a legal issue because the Act is very clear that it says ‘within’ – it doesn’t matter if (somewhere outside the consultation area) only gets it four times a week, or even once a week, they should have been consulted.

“It could put the SHA in a very difficult position.

“If fluoridated water goes outside these areas they have breached the consultation structures because the key word is ‘within’.”

At the time of going to press the SHA had failed to answer questions from the Daily Echo over whether it believes the scheme could operate legally outside of the area consulted, or if it has made any contingency plans for Southern Water concluding the initial proposals are unworkable.

In a statement the authority said: “The fluoridation consultation was based on a high level feasibility study conducted by independent water engineers.

“To progress to the next stage of implementation Southern Water need to do a more detailed technical assessment. Further information should be available in the next three months on the outcomes of this next phase.”