If true, 14 million Britons or 24% of the population will have more than a passing interest in the St Patrick's Day festivities on Saturday.

The desire to be Irish is most prevalent among young people. Almost half (42%) of those in the 18-34 category claim to have Irish ancestry.

But although many hold passionately to their Irish roots, more than half are probably exaggerating or even lying, say the authors of the report.

Dr Roy Bradshaw of Nottingham University's School of Geography, said: "A quarter of the population claiming Irish roots may be true, but you would have to go a long way back to find it, probably to the first half of the 19th century when a lot of Irish labourers came to Britain to work on the canals.

"The survey does seem to suggest that being Irish is associated with achievement in economic terms with the Celtic Tiger and in popular culture, where as in the past this may not have been the case."

Irish ancestry

The highest concentration is in London where more than three-quarters (77%) claim to have Irish roots.

Michael Coughlan, the editor of Ri-Ra, an Irish cultural magazine in London, said: "It has a lot to do with identity and culture. Irish culture - perpetuated through music, dance and literature - is a very vibrant one.

"Young Londoners are attracted to this as many perceive themselves as having no identifiable culture of their own."

A quarter of all Scots said they owed their ancestry to Ireland, while less than one in six (15%) in Wales said they had Irish roots.

The survey, carried out by Guinness and ICM Research, is a major fillip for a 'Be Irish, Be Counted' campaign for this year's census, which will have an Irish tickbox for the first time.

Various Irish organisations in Britain are urging those of Irish background to declare their ethnic identity in the survey.

Campaigners said the census question relates to ethnic identity rather than nationality and those who consider themselves British, but have Irish roots can still tick the Irish box in the census.

Sean Hutton, of the Federation of Irish Societies, told The Irish Post: "What is important, from the point of view of the census, is whether people regard themselves as of Irish 'cultural background' (the actual terminology of the Ethnic Group Question) or not."

He said the census was not just a matter of head counts, but was vital in formulating government policy for the next 10 years and targeting support especially at the large number of disadvantaged, elderly Irish people in Britain.

"Census data plays an important role in policy formation, so we need to secure good data to raise the particular profile of Irish performance and need in Britain," he said.