It is the latest drama in the growing row over the future of the Welsh language and in-migration into Wales, sparked six months ago by fellow Plaid Cymru member Seimon Glyn.

Simon Brooks: Communities under threat

Mr Glyn was publishing a book of letters of support for his remarks at the National Eisteddfod in Denbigh in north Wales, saying he remained unrepentant.

Gwynedd councillor Seimon Glyn sparked the controversial debate earlier this year when he said that Welsh speaking heartlands were threatened by a tidal wave of English speaking people.

Meanwhile, his party is looking into an article which quotes the vice president of Plaid Cymru's Ceredigion branch on the issue.

Writing on an internet chat site, Gwilym ab Ioan is reported as saying Wales is becoming a "dumping ground for England's oddballs and misfits."

Plaid Cymru has said it will not be pushed into a knee-jerk reaction, but will take action if necessary.

The party's chief executive Karl Davies said: "If he continues to use such language then his membership of the party will certainly be brought into question by many people."

"Any individual that continues to make gratuitous comments which are offensive to large sections of our community has no place in Plaid Cymru."

At the National Eisteddfod in Denbigh in north Wales, a book of letters sent supporting Councillor Glyn's outspoken comments were published on Wednesday.

But Seimon Glyn denied that his intervention was aimed at pitting Welsh-speaker against non-Welsh speaker.

"What I am saying is that if we don't do something about this issue now it will be the end for Welsh communities," he said.

The question marks hanging over the future of the Welsh language and communities were placed centre stage at the Eisteddfod on Tuesday by the intervention of a former chairman of the Welsh Language Board.

What I am saying is that if we don't do something about this issue now it will be the end for Welsh communities

Councillor Simon Glyn

First Minister Rhodri Morgan condemned as "inflammatory" the remarks made by John Elfed Jones in the Welsh political magazine Barn, claiming "outsiders" coming into Wales were the equivalent of "human foot-and-mouth disease"

Mr Morgan warned Plaid Cymru not to "pander" to alleged extremism and risk shattering the consensus on the Welsh language.

Plaid has declined to discipline outspoken Gwynedd councillor Simon Glyn, who attacked the party leader Ieuan Wyn Jones as a "coward" for failing to address the issue of inward migration.

Two thousand copies of the book have been published

Mr Glyn had called English migrants a "drain on resources" and in June, members of the pressure group Cymuned signed a declaration calling on politicians to implement "crisis measure" to save the Welsh language.

But at Denbigh on Wednesday Mr Glyn launched the collection of letters under the Cymuned umbrella which he helped set up at a meeting in a small village on the Lleyn Peninsula in north Wales six weeks ago.

A 2000 print run of the first edition of the book has been made with the aid of backing from the Books Council of Wales.

While there have been moves to calm the heated debate over the language, supporters are planning a rally on in-migration at the Eisteddfod on Friday.

Speaking on the Maes, editor Dr Simon Brooks said the book offers "solid evidence" that there is a crisis of language and culture in our traditionally Welsh speaking communities.

He said the future of those communities was threatened by the fact that young people who speak the language were unable to buy affordable housing and remain in them.