A survey has found that nearly 80 percent of primary pupils in schools across Britain have a different mother tongue, with English being a foreign language.
The survey also revealed that children who speak English as their first language are in a minority in inner-city London schools.
In Birmingham, Bradford and Leicester more than 40 percent of pupils across all primary schools do not count English as their first language, and nationally, it is a foreign tongue to nearly one in six youngsters in primary schools.
The figures have almost doubled during the past decade and are projected to increase to 23 percent - 830,000 out of 3.5million - by 2018.
There are concerns that the increases will place school finances under strain, as a growing number of youngsters require help with English.
MigrationWatch, which conducted the study using figures from the Office for National Statistics, believes that over the next five years more than 500,000 extra school places will be needed for the children of immigrants who arrived in Britain after 1998.
This will cost the Treasury 40 billion pounds, equal to a penny in the pound on the basic rate of income tax.
Sir Andrew Green, chairman of MigrationWatch UK, said the trend will lower education standards for native English-speaking children.
"These pupils will of course continue through the education system but it is primary schools where the effect is being felt most acutely at present and where English-speaking children are bound to suffer as immigrant children require extra help," the Daily Mail quoted him as saying.
azel Blears, a Communities Secretary under Labour, who was involved in the party's immigration policy, said the figures should be treated with caution.
"They may be first-generation immigrants and their parents may not speak English, but they [the children] might do," she said.
"That said, you have to recognise that where you have a large surge in the number of people coming from other countries then you have to deal with that by, for example, having more teaching assistants," she added.