Standing stones that are 5,000 years old are helping to boost the Western Isles economy by £4m a year, according to a new report.

The Comhairle nan Eilean Siar-commissioned analysis found the archaeology currently brings in around £4m and supports 80 full-time jobs.

But the island's Sustainable Development Committee heard it has the potential to be worth £8m and sustain 160 jobs.

Among the historic highlights in the Outer Hebrides are the Callanish Standing Stones, Dun Carloway and the Gearrannan Blackhouse Village.

Plans have now been put forward to help bring in more growth through the development of a trail linking the most prominent sites.

Sustainable Development Chairman, Donald Crichton, said: "Archaeology is of significant benefit to the Islands and its development offers opportunities for economic growth but that will require time, commitment and investment".

The study's findings are an assessment of the value of tourism by those with an interest in archaeology.

A number of prehistoric stone circles can be found on the Outer Hebrides, the most famous being the Callanish Standing Stones.

For five millennia they have stood on the west coast of the Isle of Lewis, made of a metamorphic rock estimated to be around 3 billion years old.

A few miles away is Dun Carloway - one of the best preserved Brochs, a circular stone building, in Britain.

Although uncertainty still surrounds why they were constructed, it is accepted by many they were the homes and defensive forts of wealthy and powerful families during the Iron Age.

The study compared engagement with sites in the Western Isles with those Orkney to find the future potential of archaeology as an economic and tourism driver.

Over a 10-year period, the study predicts an uplift of 10% in holiday visitors specifically attracted to the Outer Hebrides to engage with with its historic structures.

There is also an assumption of an increase in the numbers of existing holiday, visiting friends and family as well as business visitors being attracted by the archaeology.

The report recommends several steps to help generate growth, including the development of an archaeology based Outer Hebrides-wide trail.

This would see a route created of key places, the development of online and paper based promotional materials, installation of interpretation and improvements to access and facilities in some locations.

An application is being made to the Heritage Lottery Fund's Great Place Scheme to assist with developing tourism and public engagement.