The report was prepared by inspector David Neal, who was dismissed by Home Secretary James Cleverly last month for leaking part of it.
The report said 1,234 visas were issued to a small firm with just four employees.
The inspector said in his report that checks on care workers were "wholly inadequate" and that there was only one compliance officer for every 1,600 employers licensed to employ migrants. "In these two examples alone, thousands of people may have come to this country and been encouraged to work outside the visa requirements at the risk of hardship or poverty," Neal said.
Regarding the 275 sponsorships granted in April 2023 for a non-existent care home, the Home Office said in a statement that the visas were "issued on behalf of a genuine care home without its knowledge using false information and evidence."
The rush to fill staff shortages with foreign labor has also created a system that "invites large numbers of low-skilled workers into this country who risk exploitation."
