Migrants who can’t speak English are able to buy documents showing they have passed a vital language test, an investigation has found.
The documents, required for migrants to obtain British citizenship, are reportedly being sold by one examination centre in London for £500.
The Home Office has said it will carry out a full investigation of the findings, which could lead to criminal prosecutions for fraud.
"The Home Office takes any allegation of fraud extremely seriously and we have already begun a full investigation," Immigration and Security minister James Brokenshire told the Daily Mail.
"We will take the strongest possible action against anyone who is found to have abused the rules - including the possibility of criminal prosecutions for fraud."
The Daily Mail said it carried out the investigation into the examination centre at Upton Park, east London, following a tip-off from a whistleblower.
The centre, which has passed 50,000 candidates, is run by Learn Pass Succeed (LPS) which has four offices in London and describes itself a “modern, accredited institution” on its website.
Last night, Uzwan Ghani, one of the directors of LPS, said he was “shocked” by the paper’s findings.
"I'm shocked that this has happened and am very concerned as to how it could have happened," he added.
"We are very thorough when it comes to checking IDs of candidates before they take the test, so I will have to investigate which of the centres the test was taken in and who the assessor was.
"I've been in the business for five years and I've never come across something like this and I would not allow it. It is wrong and ridiculous”.