An inquiry has been launched into allegations of Home Office delays in providing EU citizens with the paperwork needed to work and access basic services in the UK after Brexit.

The Independent Monitoring Authority (IMA) — the watchdog set up to look after EU citizens’ rights in Britain – said it had opened the investigation after it received a “number of complaints” from people left waiting for documents after applying to the EU Settlement Scheme (EUSS).

Applicants are meant to be given a certificate “immediately” which acts as proof of their application and evidence of their rights so they can work, rent or access benefits while the Home Office considers their request for permission to live in the UK now freedom of movement with Europe has ended.

The inquiry will seek to establish whether the department has “fulfilled its obligation” to immediately provide certificates of application and assess whether any incidents could amount to a breach of the withdrawal agreement as well as considering the impact on those who have experienced delays.

The IMA, which has the power to take legal action against the Government, is expected to interview officials and review policies and processes adopted by the Home Office as part of the probe.

Chief executive Kathryn Chamberlain said the watchdog recognises “the potential impact this important issue could have on people’s lives and their rights,” but warned the inquiry “will not lead to results overnight” as she urged people to come forward with information by August 8.

Campaign group the3million said it has been warning of the “issue with serious implications” for some time.

In a statement on Twitter, the group said: “Since last year, we have received numerous reports of people losing work, housing, access to healthcare, and more.

“Proof of your application is vital to living in the UK. It’s so important that the withdrawal agreement requires them to be issued immediately once you submit your application. Despite this, the UK is slow to issue certificates causing so many problems for people.”

The Home Office said it would work with the IMA on the inquiry and consider its report once completed.

A spokeswoman added: “The EU Settlement Scheme has been an overwhelming success, with more than 5.8 million grants of status made.

“We have been working as quickly as possible to ensure those with valid applications receive their certificate of application which can be relied on to demonstrate their rights.”