The cost of giving Southampton residents a vote over controversial plans to build a giant power station close to homes has rocketed to 15 times the original estimate.

The spiralling bill for the public vote on the planned biomass plant at Southampton docks has meant even campaigners fighting the scheme now do not think it should be held.

No Southampton Biomass last night called on council bosses to ditch the so-called “preferendum”, which would have no legal impact on the proposals.

Southampton City Council had originally set aside £5,000 for the vote on the energy firm Helius’ proposals to build the 100-megawatt facility.

The true cost of balloting people in the Millbrook and Freemantle wards was later estimated to be £45,000, but the authority now admits it might need to spend up to £75,000 on the referendum.

Councillors will vote on Wednesday on whether or not to continue with the planned vote, and set aside the money from the cash-strapped council’s budget.

Members of the campaign group said they are “grateful” for the council’s support in their battle over the plans, but said they would rather see the money put to better use.

In a statement, No Southampton Biomass said “These funds should not now be used on a referendum that will have no legal weight in any future Helius application if this precludes money from being spent on external expert legal/planning advice.”

They said committing money to hiring expert advice would “send a message” that the council “means business”, and fear continuing with the vote plans would mean no money for the rest of the campaign. Fears have also been raised that spending so much public money “on something that ultimately will not affect the planning process” could backfire and have a negative impact on the battle.

Freemantle ward councillor and Southampton’s deputy Tory leader, Jeremy Moulton said: “It appears the principle is more important than the cost, because they want to be the first in the country to take advantage of the new powers under the Localism Bill.

“It does beg the question if it’s value for money when it has no legal weight. We support the principle, but aren’t happy about the cost.”

Council leader Cllr Richard Williams was last night unavailable for comment.