The plans for the lake had been recommended for approval before the board meeting, which was held this week, but councillors decided to leave making a final decision until they had more details.

The cost of the restoration work – which the council hopes will prevent a repeat of what happened in July 2006, when thousands of fish died – originally stood at £360,000.

But the matter went before the board this week as the cost had risen by £83,000 after the council had sought 'expert opinion' on the implications of the work.

At the board meeting this week, Chris Conroy of engineering consultants, Capita Symonds, said: "Once the work has been carried out, there will be more oxygen in the water, meaning we should not have a repeat of summer 2006, when tonnes of fish died.

"The hot temperatures and low level of the water meant that a blue-green algae, toxic to humans, starved the lake of oxygen, killing carp valued up to £600."

Some members of the board expressed concern at the price increase, saying they would find it hard to justify the cost to constituents.

Cllr Bob Davey said: "How are we going to tell the public we are going to spend this much on the lake? First the cost was in the £300,000 range, now it is £400,000, what if it went up again to £500,000?"

Cllr Wynne Jones added: "This is a high sum of money and I am not sure all the options have been looked at in full.

"For a start, what if we spent this money and the same thing happened again? There seems no guarantee this will completely rectify the problem."

Cllr Leslie Davies said the development would have a huge impact on the town for the right reasons.

"This is an integral part of the town's regeneration plans. It will have a huge impact on tourism and the economy, but I do agree we need more details on this, such as a business plan," he said.

Members agreed to defer making a decision on the matter until April's board meeting, where they will be presented with extra information from Capita Symonds.