Almost two in five Syrian asylum seekers were made to take a widely criticised language test to prove their nationality, the Guardian can reveal.

Campaigners and experts have criticised the Home Office for the widespread use of language analysis on those claiming to have fled Syria, describing it as “pseudoscience” and a political tool to exclude migrants.

The tests are used to determine asylum seekers’ country of origin by profiling aspects of their speech, and should be carried out by experts familiar with the language. Current guidelines state language analysis should generally be used where applicants cannot produce reliable and accepted documents.

A Guardian investigation has found:

The Home Office used language analysis tests in cases where visas had been issued or reliable documents existed.

An author of a report produced by the company Verified AB, which was used by the Home Office to dispute the nationality of a Syrian asylum seeker, could not speak Arabic.

One report by Verified AB cited speech that did not exist in the audio recording.

Analysts at the company Sprakab failed to make allowances for minors in some cases and in one case incorrectly recorded a minor as an adult.

The Home Office contracts two private companies, Verified AB and Sprakab, to run thetests on asylum seekers. The department carried out 5,900 language analysis tests between 2011 and 2018, according to information obtained through freedom of information requests.

More than two-thirds of all tests – about 3,900 – were done in cases where the applicant claimed Syrian nationality. Syrians accounted for 5% of all asylum applications in this period.

Between 2011 and 2018, 10,255 Syrians applied for asylum, according to Home Office statistics, meaning almost 40% of all applicants were tested.

Yaron Matras, a professor of linguistics at the University of Manchester, said: “There’s been suggestions from academics and activists that the use of language analysis is a political way of excluding people. I’ve certainly found there is that risk because there’s a lack of diligence when commissioning private contractors to do that.”

Matras, an expert in Arabic and Kurdish, has provided testimony in court and helped overturn more than a dozen decisions in the past three years where the Home Office relied on language analysis to refuse asylum.

After first publication of this article, Roderick Martin, a spokesperson for Verified AB, of Sweden, said that in Verified’s case one or more trained native-speaker analysts always contribute to an analysis report, along with the professional linguist who oversees and signs the report. This combination of native speaker and linguist, he said, is the method sanctioned by IAFPA, the International Association for Forensic Phonetics and Acoustics. [See footnote]

Ahmed, 28, who did not wish to give his real name, came to the UK on a student visa in 2015. Before this he had lived in Syria until the age of four and later Dubai.

When he applied for asylum in 2015, he was asked to do a language analysis test, despite having a range of documents and the visa as proof of his identity. “I’ve got nothing to hide. I am Syrian, both my parents are Syrian. And I couldn’t go back to Syria because the situation is horrendous. But this did feel discriminatory,” Ahmed said.

In another case, 31-year-old Zahra, who did not want to give her real name, arrived in the UK on a student visa in 2015 with a scholarship exclusively given to students from the Levant.

Despite providing her passport and other documents for her visa and scholarship, Zahra was asked to undertake language analysis. “I had everything with me, original papers in very good condition. I’m not sure if they did this randomly or if they targeted people,” Zahra said.

Mohammed Ateek, a teaching fellow at the University of Reading, who researches language and migration, said: “The use of language analysis on applicants with valid documents or UK visas doesn’t leave any space for doubt that it has been used in a discriminatory manner.”

The Labour MP Thangam Debbonaire, who chairs the all-party parliamentary group on refugees, said: “According to this investigation, language analysis tests are being used even when other documents are available. This is worrying, considering that it is such an imprecise method for assessing where people come from.

“We should not rely on such uncertain assessment methods when other information is available. To do so risks sending people back into danger. I will be writing to the home secretary to ask about this.”

Chai Patel, the legal policy director at the Joint Council for the Welfare of Immigrants, said: “The fact that caseworkers are continuing to use discredited pseudoscience to reject asylum claims is hardly surprising. But the problem isn’t one of science or technology, it is that the Home Office is culturally and institutionally incentivised to deny protection to those fleeing persecutions.

“Politicians need to take responsibility for the culture they have created through their dehumanising language around refugees, and work to rebuild the Home Office from the ground up.”

A Home Office spokesperson said: “Language analysis testing is just one piece of evidence used as part of the consideration process to ensure genuine refugees receive our support. It can provide a speedy resolution to claims by helping to confirm an asylum applicant’s place of origin, and its use in immigration cases has been supported by the courts, including the supreme court.

“Asylum caseworkers follow the published guidance on the use of this testing and carry out routine quality checks to ensure compliance.”

Roderick Martin of Verified said that his company’s method – Linguistic Origin IDentification (LOID) – was supported by “observations and detailed references to scientific literature. Verified includes a clear account of the limitations of the method as well as the cautions that should be taken into account where each language test is concerned.” The method, he added, “does not operate with geographical communities or nationalities, but with linguistic communities – dialects – which can sometimes straddle borders”.

The spokesman said that Verified did not operate with geographical communities or nationalities, but with linguistic communities, which can sometimes straddle borders.

• This article was updated on 3 July and 10 July 2019 to: include additional comments from Verified AB; specify companies in some examples; and clarify that language analysis reports can have multiple authors.