The archdruid of Wales has accused English people of "swamping" Welsh values when they move to Wales.
Robyn Lewis last year became the first archdruid to be elected
Robyn Lewis reopened the long-running controversy over the future of the Welsh language by claiming that people from England thought their culture was superior and wanted to "colonise" their neighbour.
Dr Lewis said he was made to feel uncomfortable because he spoke Welsh in the traditional Welsh-language heartland of the Lleyn Peninsula, in the north-west of the country.
He is the latest in a series of public figures in Wales to criticise the impact of English-speaking incomers on Welsh language areas.
Dr Lewis, who is also known by his archdruidic name of Robin Llyn, told BBC Radio Wales that he used the words colonise and swamp deliberately.
He was responding to a survey showing that the town of Pwllheli has had one of the sharpest increases in price rises in Britain - 85% in the past two years.
Dr Lewis said: the names of houses and businesses in Pwllheli had been changed from Welsh to English.
Pwllheli is one of the main towns on the Llyn peninsula
"There is an influx of people from elsewhere into this area," he told the Good Morning Wales programme.
"One doesn't object to the actual influx but one does object to the scale of it.
"Margaret Thatcher once said that she didn't mind immigration, but it was the scale of immigration that was going to swamp English values, as she called it.
"Well, this is swamping Welsh values.
"You go into a shop and people frown at you, they glare at you because you speak Welsh. One feels uncomfortable in one's own milieu.
"These people don't come in to absorb the culture, they don't come in to integrate. They come in to colonise and I use the word colonisation deliberately."
"They bring parts of Lancashire into Lleyn. What else is that but colonisation?
"They want us to become like them. In organisations in Lleyn, Welsh is supplanted by English and we have to conduct these things in English to suit them.
"Now if that isn't colonisation I don't know what is. They think their culture is superior and they impose it upon us."
House prices have risen in Pwllheli by 85% since 2001
The price boom led to the language pressure group Cymuned picketing an estate agent last year until it agree to allow people to market their homes only to existing residents.
But local estate agents have defended the influx of new homeowners, saying that the wealth they had brought to the area benefited everyone and allowed local people to make large profits from their homes.
"Too much is said about poor local people not being able to afford houses," said Stephen Tudor, a chartered surveyor and partner in a local firm of estate agents.
"There's an element of catch-up going on and homes are still affordable."