The UK has failed to pass on the details of 75,000 convictions of foreign criminals to their home EU countries and concealed the scandal for fear of damaging Britain’s reputation in Europe’s capitals, the Guardian can reveal.

European trust in the UK on security issues sank to a new low on Tuesday night after details emerged of the apparent cover-up, which prompted calls for an investigation in the UK and a warning from one senior MEP that a Brussels inquiry was inevitable.

The police national computer error, revealed in the minutes of a meeting at the criminal records office, went undetected for five years, during which one in three alerts on offenders – potentially including murderers and rapists – were not sent to EU member states.

Authorities in EU countries were not informed of the crimes committed, the sentences given to their nationals by UK courts or the risk the convicted criminals posed to the public.

Because the details were not passed on, dangerous offenders could have travelled back to their home countries without the normal notification to local authorities of their presence.

Such is the scale of the scandal that the Home Office initially chose to conceal the embarrassing failure from EU partners.

Minutes of an ACRO criminal records meeting last May – deleted from the ACRO website after the Guardian story was first published – state: “There is a nervousness from Home Office around sending the historical notifications out dating back to 2012 due to the reputational impact this could have.”

A minute of a meeting held the following month said: “There is still uncertainty whether historical DAFs [daily activity file], received from the Home Office, are going to be sent out to counties (sic) as there is a reputational risk to the UK.”

Asked if the Home Office had resolved the problem in the seven months since the second meeting, a spokesman said: “Work is already under way with the police to resolve this issue as quickly as possible.”

The historical backlog of 75,000 notifications has still not been sent to European law enforcement agencies, sources confirmed. “It’s an ongoing glitch that we need to fix. We are working towards getting that done,” one insider admitted.

The shadow home secretary, Diane Abbott, joined calls for a “full urgent investigation” into the decision to keep the blunder from European partners, with the Liberal Democrats saying the Home office had “serious questions to answer”.

Abbott told the Guardian: “It is bad enough to have made serious errors in relation to sharing information on criminals, but it seems that there was also an attempt at a cover-up.

“Ministers need to come clean. When did they know about these failures, why did they not make them public, and how are they going to prevent any repetition? A full, urgent investigation is needed.”

Yvette Cooper, the chair of the home affairs select committee in the last parliament, called the revelations “deeply disturbing”.

“We need to know whether that decision not to immediately pass on criminal information has put public safety at risk,” she said. “The Home Office needs to explain why they did not immediately pass that information on as soon as the error was discovered. To put their reputation ahead of public safety would be highly irresponsible and risks undermining crucial international crime fighting relationships.”

The revelation comes ahead of crucial negotiations with the EU over the future security relationship with the UK, with Britain’s reputation as a trustworthy partner already having come under serious question.

This month, the European parliament’s justice and home affairs committee was given evidence of “deliberate violations and abuse” by the UK of the Schengen Information System (SIS), an EU database used by police and border guards across the border-free Schengen zone.

The British authorities had made “unlawful” full or partial copies of the database that were said by an EU report to pose “serious and immediate risks to the integrity and security of SIS data”.

Sophie in ’t Veld, a Dutch MEP on the European parliament’s committee on civil liberties, justice and home affairs, said she expected an urgent inquiry by a European parliament justice committee, adding the issue would be raised with the European commission in a resolution.

She said: “This is yet another scandal that casts a very dark shadow over security and law enforcement cooperation. This cover-up could have exposed EU countries to security risks and should urgently be investigated by the Schengen scrutiny group in the European parliament.

“Certainly, we will add this to the already long list of issues that need to be discussed with the UK in the context of the future relationship.

“This revelation of the failure to alert authorities on criminals and the cover-up afterwards casts serious doubts on the UK as a reliable partner.

“The purpose of information exchange is enhancing security. If one side fails to deliver, security gains are zero and cooperation pointless.”

An EU official agreed that the issue would impact on the level of trust in the UK. The source added that the revelations also undermined British claims that a British loss of EU databases would prove mutually disadvantageous.

During the negotiation over the post-Brexit relationship, the government will seek to convince Brussels that there should be continued data exchange with British authorities, operational cooperation between law enforcement authorities and judicial cooperation in criminal matters.

The UK will no longer be a member of Europol and its police and security services will lose access to key EU databases at the end of the transition period in December 2020.

Officials believe the failure to alert EU partners is down to the police national computer, a database containing information on millions of convicted criminals and their jail records.

It generates daily activity files of the latest updates, and any relating to foreign offenders are meant to be forwarded to the European Criminal Records Information Exchange System (ECRIS) by a body known as ACRO Criminal Records Office, responsible for international police data sharing.

Last year, ACRO realised that a large number of the alerts that should have been given to foreign countries had been missed, many of which covered convictions of criminals who had dual nationality.

ACRO’s strategic management board was briefed last May about the “ongoing issue dating back to 2015 regarding notifications out for foreign nationals and that the current DAF reports are missing about 30% of foreign nationals”.

The board was warned that an estimated 75,000 checks had not been done over the years.

A spokesman for ACRO said: “ACRO relies on the daily activity files from the police national computer to send notification messages to other countries in relation to cases where one of their nationals has been convicted in the UK.

“The issue arose when it was noticed that not all relevant DAFs were sent to ACRO, for example in cases where the subject had dual nationality.

“As a result, a software script has been developed at Hendon, the PNC headquarters, and is due to be released in the next software update schedule (the date of which is yet to be confirmed).”