Six Indian IT services firms recruited a total of 11,644 immigrants to work for them in the UK in 2006 alone, according to government figures obtained by the Sunday Telegraph.
The disclosure to the paper, under the Freedom of Information Act, comes as the government seeks to reform the work permit scheme, which could lead to "non-essential" IT workers being kept out of the UK.
Peter Skyte, national officer of the Unite union, told the Sunday Telegraph, "It may be that there are skill needs that can be filled by overseas workers but this should not be at the expense of resident workers.
"Questions need to be asked about how this is happening and whether companies are using the current work permits system to undercut pay rates in the UK."
The IT work permit figures for 2006 are the latest government figures available, and the numbers may well have gone up since then, in line with the expansion of Indian outsourcing companies responding to increased UK outsourcing demand.
Over a seven-year period, the six companies - Tata Consultancy Services, Wipro, Mahindra-BT, Mastek, Infosys Technologies and Satyam Computer Services - were granted work permits to bring 47,000 foreign nationals into the UK.
The annual total has climbed steadily every year since 2000 and has doubled since 2003, says the Telegraph.
Most of those coming into the UK are thought to have been Indian nationals. The Home Office figures do not record how many have stayed in the country and how many have returned to their own country.
Tata, the largest Indian IT services firm, secured the largest number of permits. It was given 4,000 permits in 2006, a big rise on the 1,600 issued in 2000.
The government figures include staff both on short-term and long-term work permits. Immigrants who live and work in Britain for five years continuously have the right to apply for permanent settlement rights.
IT union opposition to the existing work permit scheme has been consistent: