Concerns that a second pipeline may be built across unspoilt Welsh countryside have surfaced, after a Plaid Cymru MP got hold of a recent consultation document produced by the National Grid.
Plaid Cymru's Adam Price said that the National Grid consultation document, made for the benefit of the gas industry, revealed that a second pipeline - to be built across Wales to deliver energy to the west of England - was being considered.
But the National Grid denies the allegations and says that Mr Price has come to the wrong conclusions.
The first pipeline, which will transport liquid gas from Milford Haven to Tirley in Gloucestershire, has been delayed after direct action protests.
The consultation report states that " in the event that incremental capacity is offered and allocated above (the existing maximum level), National Grid NTS would be required to deliver further additional investment to increase the network capability in the Milford Haven area.
"This would include the design and construction of a duplicate of the connecting pipeline that is currently under construction to extend the National Transmission System."
A National Grid spokesperson said that the report consultation paper contained several "purely hypothetical" examples, which were used "only for illustrative purposes".
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