Immigration may be threatening Britain's status as a country, it has been claimed .
A pamphlet by social policy think-tank Civitas said the UK may already have reached a "tipping point" where it can no longer be regarded as a single nation.
Author David Conway said that if Britain has become a "nation of immigrants" it could lead to political disintegration.
The 100-page booklet said: "Those for whom this country has always been a model of tolerance and freedom cannot but have cause for deep concern about the seemingly reckless pace and scale on which immigration has recently been allowed to proceed.
"As a result of it, the country may possibly have already reached a tipping point beyond which it can no longer be said to contain a single nation.
"Should that point have been reached, then, ironically in the course of Britain having become a nation of immigrants, it would have ceased to be a nation.
"Once such a point is reached, political disintegration may be predicted to be not long in following."
Mr Conway, senior research fellow at Civitas, disputed a claim made by the Commission for Racial Equality in 1996 that "everyone who lives in Britain today is either an immigrant or the descendant of an immigrant".
The author said: "The view that Britain is a nation of immigrants suggests Britain has always experienced immigration on its present-day scale from time immemorial, which is by no means the case."
Previous waves of immigration such as the Normans, the Huguenots and the Jews each represented 1% or less of the overall population of the country at the time, he added.