Plans were announced yesterday for a new multi-million pound gas pipeline running through the Welsh and English countryside - transporting about 20 per cent of gas needed to meet UK consumption.

National Grid said that the preferred corridor of its gas pipeline will run from Felindre, near Swansea in south Wales to Tirley, between Newent and Tewkesbury in Gloucestershire.

The body, which said it has taken environmental considerations into account, anticipates that more than 1,000 people will be working on the project at the peak of construction and while many will be specialist engineers, where possible others will be recruited locally.

The pipeline, due for construction in 2007, is the second phase of the National Gas Transmission System reinforcement required to transport natural gas from two liquefied natural gas (LNG) terminals under construction at Milford Haven in west Wales.

Liquefied gas will come into the port in tankers and will be "re-gasified" before entering the national pipeline network.

Once complete, the pipeline will transport about 20 per cent of gas needed to meet UK consumption, National Grid said.

The 115- mile, 48- inch diameter steel pipeline will start at a new compressor site in the Felindre area, taking a north westerly route, crossing the River Loughor northwards before following the A483 from Ammanford to the north west of Llandeilo. It will then cross the River Towy, traverse the north-west of the town and follow the A40 north east, crossing the River Towy again to the north of Llangadog.

The pipeline then goes east towards Brecon, before turning north to follow the A470 and A438 to Hay-on-Wye. It then travels south east in the direction of the B4348 where it crosses the A465, continuing south east towards a new valve compound at Peterstow, to the west of Ross-on-Wye, close to National Grid's existing compressor station.

The route then moves east, north of the M50, passing under the motorway near Junction 3 (Newent), ending in the Tirley area.

National Grid project manager David Mercer said: "This pipeline is an important addition to the National Gas Transmission System and an essential requirement to provide the UK with reliable and efficient gas supplies.

"Identifying a suitable route has been an extremely lengthy and complex process. We have carried out a detailed assessment of the route options and worked closely with the statutory environmental consultees.

"The preferred corridor provides the best balance between environmental impact, land use and construction requirements. As far as possible we avoid areas of population, taking into account environmental, geological, and archaeological features and construction, health and safety considerations.

"National Grid is committed to minimising the temporary construction impacts, and to carrying out the highest quality reinstatement on completion of the work."

Having identified the preferred corridor, National Grid said it will be working closely with landowners to agree the best route possible, and carrying out a full Environmental Impact Assessment before applying for consent to build the pipeline.

To minimise the potential effects of construction, National Grid will use trenchless techniques, such as tunnelling, to cross several major roads and rivers.

This should ensure that river beds are undisturbed and that there is minimum effect on the environment, the body said. Where an open-cut road crossing is unavoidable, it will be carried out in close liaison with the local council and completed as quickly as possible.