Mrs Macmillan said Oban was one of the communities affected

She has written to Scottish Water to highlight difficulties experienced by places such as Aviemore, Boat of Garten, Skye and Lochalsh and Taynuilt.

Scottish Water said the region would benefit from �160m of new investment.

A spokesman said it would take time for all connections or extra capacity at treatment plants to happen.

Mrs Macmillan said: "I have raised this issue several times in the recent past as the lack of Scottish Water infrastructure has been a hindrance to housing and other developments across the Highlands and Islands.

'Communities suffering'

"Scottish Water was recently allocated substantial funding from the Scottish Executive through the Quality and Standards III programme.

"However, in recent weeks and months I have received letters from constituents across the Highlands, including Aviemore, Boat of Garten, Skye and Lochalsh, Kiltarlity, Oban and Taynuilt.

"All the correspondents highlight the effect that the lack of water and sewerage infrastructure is having on development plans for their respective areas."

The Labour MSP has asked the chief executive of Scottish Water what was being done to resolve the current difficulties.

Scottish Water said the communities would benefit from a share of �160m for Scotland to help the development of housing.

'Big job'

Spokesman Jason Rose said they were embarking on a new list of financial priorities - and they would provide the infrastructure where the demand was.

He added: "It is over to us now - it is our job to deliver.

"The executive has made this very clear that it's up to Scottish Water to deliver the improvements that these communities are looking for."

Mr Rose said that the organisation faced a tough job balancing demands from different communities.

He said: "Some connections are going to happen this year, some are going to happen in four years' or eight years' time.