The Federation of Irish Societies in Britain is to seek the inclusion of an "appropriate" question in the 2011 census to try and accurately calculate the number of Irish living there.
The federation represents 115 member organisations in England, Wales and Scotland.
In a submission yesterday to the meeting in Edinburgh of the British-Irish Inter-Parliamentary Body, the federation said it believed the 2001 figure of 675,400 Irish from the Republic and the North was a gross underestimate.
The federation's chairwoman, Sligo-born Dr Mary Tilki, said this figure should be multiplied by three or four. She defined Irish as Irish-born and second- and third-generation Irish.
This census data, Dr Tilki said, should be used to inform government policy in Britain. The Irish, she said, experienced significant disadvantages in Britain, particularly in the areas of health, housing and access to services.
In addition, she said, elderly people who wanted to return to Ireland had difficulty getting housing and benefits, given the difficult bureaucratic processes that were involved.