Rich Londoners looking for second homes are destroying the Welsh language, protesters say

To the estate agents, it was an inoffensive piece of marketing blurb about "outstanding country house in a delightful situation". But for Angharad Price and her supporters it was yet another example of crass colonialism by an invader.

To the estate agents, it was an inoffensive piece of marketing blurb about "outstanding country house in a delightful situation". But for Angharad Price and her supporters it was yet another example of crass colonialism by an invader.

Ms Price and about a dozen like-minded souls stood in the rain outside the offices of a property dealer in London's Mayfair yesterday to protest against the house price boom they say is threatening to eradicate Welsh-speaking culture.

The demonstrators, members of the pressure group Cymuned – Welsh for "Community" – are calling for a halt to an influx of wealthy Londoners and other English buyers of second homes who they say are pricing local residents out of their towns and villages.

The focus of their anger was the headquarters of Lane Fox, a specialist in properties at the upper end of the market across Britain, which Cymuned accused of focusing on homes in Wales despite not having any offices in the principality.

Of particular concern was a five-bedroomed family home, set in an acre of gardens and woodland, in the village of Dinas Mawddwy in Snowdonia National Park, which has been put up for sale by Lane Fox for £250,000. The average salary in the area is £12,000.

Ms Price, 30, an author from Dinas, said: "It's disrespectful and damaging. It's disturbing to see a house like this for sale in Mayfair when it is not even being offered for sale in Wales. It's doing cultural and economic damage."

Simon Brooks, Cymuned's chief spokesman, said: "Mayfair is a world away from Dinas Mawddwy, which is one of the poorest places in the UK. By selling a property only outside Wales, this destroys the Welsh language – our people cannot afford homes and that means if they move out, the local language moves out with them." Property prices in rural Wales have risen by 30 per cent in the past year and about 60 per cent of homes sold in those areas are to outsiders, Cymuned said.

The pressure group wants estate agents to sign up to a "code of ethical practice" which will require all homes in Wales to be advertised solely in local newspapers and shop windows for three months after they are put on the market. It is also lobbying the Welsh Assembly for measures to provide Welsh-speaking communities with affordable homes.

Lane Fox, which has 20 offices in England, said it was not going out of its way to sell the house in Dinas Mawddwy to Londoners, pointing out that the sale was being handled by its Shrewsbury branch.

Peter Lowndes, the company's chairman, said: "We handle about two or three houses in Wales a year ... I do have a degree of sympathy with the protesters. Perhaps they should be looking at a system which offers properties of a certain price only to locals. But that is something that politicians can grant, not estate agents."