Image copyright Geograph/Christine Matthews Image caption The Craig Goch dam was built at the turn of the 20th Century to supply Birmingham

A trade union's call for water to be supplied from mid Wales to the south east of England has prompted objections from Plaid Cymru.

The GMB wants water from the Craig Goch reservoir to be transported via the Cotswold canals in case of drought.

Plaid Cymru said the Welsh Government controlled the resource in Wales and that any such proposal to help Thames Water should be "fiercely resisted".

The GMB has since apologised as it "never intended to upset anybody".

Their original comments were made as part of its campaign for the nationalisation of the privatised water industry.

The Welsh Government said it would need to be consulted on any plans.

The Craig Goch dam was built by the city of Birmingham at the beginning of the 20th Century to supply water from the Elan Valley.

The issue of water has been highly controversial in Wales since the flooding in the 1960s of Capel Celyn in the Tryweryn valley to supply Liverpool.

But, as part of the devolution of powers to Wales, the authority to make decisions on the matter is now shared between the Welsh and UK governments.

'Opportunities'

The GMB says the current restoration of the Cotswold canals in Gloucestershire should be seized as an opportunity to transfer water from the reservoir to the Thames.

A recent meeting of the GMB's Congress passed a resolution saying long term weather cycles meant London and parts of south east England "will experience periods of low rainfall that will result in reservoirs running short of water".

The resolution said: "There is no shortage of water in Britain but there is a lack of capacity to get the water from where it is plentiful to areas where it can be scarce from time to time."

Image copyright Geograph/Nigel Brown

Plaid Cymru's Arfon MP Hywel Williams said it was not up to the UK government in London or individual trade unions "to tell the people of Wales what should be done with our water".

He accused the union of trampling on an issue "they do not understand".

"The Welsh Government has control of Welsh water - any attempt at bargaining away one of our most powerful natural resources should be fiercely resisted," he said.

"If it is to be transferred to London and the south east, it should be for a proper price."

A Welsh Government spokesman said: "If there are any proposals that could affect Wales, the water company would need to consult Natural Resources Wales and the Welsh Government."

The owner of the reservoir, Dwr Cymru Welsh Water, said: "Any plans to transfer water from Wales to other parts of the UK should only be considered if it benefits Welsh customers."

'Big problem'

GMB London Region Organiser Michael Ainsley told BBC Radio's Good Evening Wales programme that the union apologises, adding they "never intended to upset anybody".

"There are problems with water shortages throughout the UK, in particular in London and the South East, and what we're starting this week is a discussion about how we're going to fix that," he said.

He added: "I certainly can't comment on what happened in the past, because it was not something I was particularly familiar with, so in that respect Mr Williams is probably correct in that we didn't know what we were treading on."

Thames Water has declined to comment.