A mobile phone app for EU nationals seeking to stay in the UK after Brexit – claimed to be as user-friendly as “an online account at LK Bennett” – will not work on iPhones, Home Office officials have admitted.

After arriving late for a meeting in Brussels to reassure MEPs of the efficiency of the British government, officials from Amber Rudd’s department conceded that a key function on the app would not work on the phone brand used by more than half of the adult population in the UK.

Catherine Bearder, a Liberal Democrat MEP who attended the meeting, said one Home Office official had suggested applicants could “borrow someone else’s” phone to complete the registration. “It is beyond belief,” Bearder told reporters.

The group of officials, who were late due to a delayed Eurostar, were in Brussels to demonstrate to MEPs the functions of the new Home Office app in order to build confidence.

Rudd had insisted that using the Home Office app would be as easy for the 3 million EU nationals in the UK as setting up an online account at LK Bennett, the clothes retailer. She also said it had been “extensively tested”, but Home Office officials admitted they had not yet begun mass testing of the app. They also said they would be hiring 1,000 caseworkers for a customer service centre for EU citizens, although they had not yet begun this process.

However, the fact that the app does not work on Apple devices has highlighted what many say is the government’s poor record with technology.

EU citizens who have tested the app say it requires just a small amount of information, such as a scan of a passport, address, email address and a selfie to match the passport picture. The system then matches the biographical details with HM Revenue & Customs records to give the applicant an instant answer as to whether their application has been successful.

However, it has emerged that because Apple will not enable its technology to read the chip on modern passports, the registration can only be completed on an Android phone.

Guy Verhofstadt, the European parliament’s Brexit coordinator, said he would be writing to Theresa May this week about a series of wider concerns, including the £72 cost of registering, and the need for every member of a family to individually apply for settled status.

Verhofstadt said: “The treatment of the Windrush generation under UK immigration law has unfortunately created renewed anxiety among EU citizens in the UK and shows why we have to get this right. The European parliament will closely scrutinise developments and work to ensure sufficient guarantees are in place to avoid the repetition of such a situation for EU citizens.”

The London MEP Claude Moraes, chair of the European parliament’s civil liberties committee, said: “In my opinion, there is a need for more investment. They need to understand the political immensity of this, they need to understand that there is no history globally of registration systems based on this technology working.”

One person in the meeting is said to have quipped: “It’s like the Irish border – they are trying to solve the problem with technology and we know it won’t work.”

Moraes added that he was deeply concerned that the government was registering EU citizens on the basis of secondary rather than primary legislation, allowing the laws to be changed in the future.

Under the withdrawal agreement, EU nationals will have recourse to the European court of justice should they have complaints about their treatment, but the scandal over the Windrush generation has illustrated the dangers in the longer term, Verhofstadt said.

It is understood that the iPhone compatibility issue was known about at the app’s inception. “We’re speaking to Apple to try and get this resolved,” a Home Office spokesman said.

In its statement, the department added that “technology will play an important role” in the identification element of registration, but it was also making “non-digital” routes available to all applicants, including sending a passport through the post.