Gwynedd’s economic chief has defended its UNESCO world heritage bid amid claims from one language group it could add to the county’s already existing “over tourism” problem.

Such World Heritage status would see the towns and villages that “roofed the 19th century world” receive the same designation as the Grand Canyon and Great Barrier Reef, in a move Gwynedd Council hopes will result in regeneration and new jobs.

On July 28 it will find out if the bid has been successful, covering the communities of Dyffryn Ogwen, Dinorwig, Dyffryn Nantlle, Cwmystradllyn and Cwm Pennant, Ffestiniog and Porthmadog and Abergynolwyn and Tywyn.

If accepted by UNESCO, the landscape will  join the Castles and Town Walls of Edward I at Caernarfon, Conwy, Beaumaris and Harlech, Blaenavon Industrial Landscape in south-east Wales; and Pontcysyllte Aqueduct and Canal near Llangollen as the fourth such site in Wales.

But one language pressure group claims that such status would only add to an existing “over tourism” issue in Gwynedd, with the authority having already published reports stating concern that the sector isn’t benefiting local communities to the extent that it should.

With tourism said to contribute over £1bn a year to the local economy, 2016 saw over seven million people visit attractions including Caernarfon’s historic castle, the mountains of Eryri and the beauty of Penrhyn Llŷn and Meirionnydd.

But a council report in February warned of an “over dependence” on low paid jobs within tourism when compared to other industries and areas of the UK, also raising concerns that the county cannot cope with “unsustainable” visitor numbers as seen in some “honey pots” last summer.

“Whatever the hope of the county council, it must be honestly acknowledged that gaining World Heritage Site status would increase tourism to the areas concerned,” said Cylch yr Iaith in a statement.

“And regarding the intention to ‘stimulate economic development’, tourism developments appear to be increasing throughout the county.”

Claiming that visitor numbers would increase and result in “more negative effects” including an increase in second and short-term holiday homes and “an English speaking influx,” they added that mountainous areas faced similar issues to coastal resorts.

“It was recently expressed that it was hoped that the slate areas would come with a different type of visitor due to World Heritage Site status – visitors with an interest in history and old industrial sites, but again it should be remembered that such visitors are more affluent overall and with the means to invest in a second home.

“The experience of other areas within the county shows how the character and language of a community are changed as a result of incompatible tourism developments.”

But in response, Gwynedd’s economic development portfolio holder said the bid was about celebrating the area’s rich past, stressing that the Welsh language would remain integral.

Cllr Gareth Thomas went on to say, “The nomination is an opportunity for us to celebrate what our communities have done – both locally in maintaining such a rich and vibrant language and culture, and internationally by providing roofing materials worldwide and transferring technology and people internationally.

“The Welsh language and culture is central to the development of the nomination and we will continue to run activities and projects to support Welsh as a communal language through the designation if successful.

“This is an opportunity now for us to be proud of our heritage and culture as we recover and the world heritage designation will be a vital vehicle in the economic and social regeneration of our communities for the future.

“The council recognises that the designation can attract new visitor markets to the area – including international visitors and visitors with an interest in our language, culture and heritage.

“These visitors would tend to visit all year, spend more and stay longer in the area – and this can benefit the economy sector by visiting local businesses.”

Although led by Gwynedd Council, the bid is a partnership between a number of organisations including Snowdonia National Park, the National Trust, Bangor University, the Welsh Government, Cadw, Royal Commission on the Ancient and Historical Monuments of Wales and the National Museum.

A decision is expected following a meeting of the UNESCO World Heritage Committee on Wednesday, July 28.