THE main contractor on the Scottish capital's controversial flood-prevention scheme is involved in a wrangle with the council over the cost of the project, which is now running a year behind schedule.

Edinburgh City Council is in talks with civil engineers Lagan Construction over the spiralling cost of the Water of Leith Flood Prevention Scheme after the bill nearly doubled in the last year.

The council said the setbacks and rising costs were due to bad weather and unforeseen land conditions.

Its officers are challenging the bill that council papers confirm stands at £21m.

This figure includes consultants' fees yet to be publicly identified, and is up from £11.5m last year, with an internal "adjudication" under way.

A council source said: "The adjudication that is ongoing at the moment is not going to suspend the work."

However, there was a call for more stringent parameters when drawing up such deals.

The process was said to be similar to the row between the main trams contractor and the council over extra costs that halted the city's trams project – where costs rose from £545m to £776m – for months.

Green Party Councillor Nigel Bagshaw said: "There is an ongoing problem with the way contracts are drafted in Edinburgh, and they need to be much tighter so the city does not enter into open-ended commitments."

The Herald revealed that the first phase of the scheme from Stockbridge to Bonnington is now not due to be completed until next autumn, meaning 12 months more disruption for hundreds of residents.

The two further stages have yet to be put out to tender but may not be realised if the Scottish Government decides not to bail out the cash-strapped council.

Officials have admitted the council does not have enough money to finish phase two of the project, from Murrayfield to Belford, and phase three, Balgreen to Longstone.

Completion of these would cost an additional £65.9m.

Mr Bagshaw, who represents Inverleith, said the scheme had been a cause of contention.

He added: "The scheme is a sledgehammer to crack a nut and comes at far too high a price in terms of monetary cost, environment damage, and the impact on the lives of those living next to the construction sites. My hope now is that the works will be completed on time so that life can get back to normal for the people of the Stockbridge Colonies and Warriston.

"As phases two and three are unlikely to go ahead we need to take a reasoned look at alternatives to protect people's homes and ensure that they can get insurance for their houses."

The council said it was in discussion with Lagan Construction Ltd, who are currently constructing phase one, over the level of additional costs for the work carried out.

It added: "Any increase in estimated cost for phase one would result in the shortfall for phase two increasing. Cost certainty cannot be guaranteed at this moment in time and it is likely that it will be at least January 2013 before an accurate figure can be reported."

Lagan did not respond to requests for comment.

A spokesman for the Scottish Government said it had a duty to fund new projects elsewhere in Scotland. He said: "The Government met Edinburgh City Council and Cosla earlier this year to discuss additional funding for the Water of Leith scheme.

"Following the meeting, Cosla and the Government agreed to consider the additional funding of existing schemes when determining the criteria to be used for allocating undistributed funding available for flood projects."