Some EU citizens living in the UK were left unable to vote during the European elections because of government delays in implementing recommended electoral changes, a new report has claimed.

The Electoral Commission’s report found some British expats and citizens of other EU member states living in the UK faced “difficulties” when trying to vote in the European parliamentary elections on 23 May 2019.

In its report, published on Tuesday, the commission said the problems were caused by the government’s delay in implementing electoral changes it had first recommended in 2014.

Bob Posner, the commission’s chief executive, said it was “unacceptable” that some EU citizens and British people living abroad were prevented from voting.

Today we’ve published our report into May’s elections. It highlights that government delays in taking forward recommendations for electoral reform led to difficulty experienced by those who wanted to vote. pic.twitter.com/n0mIOoePzx — Electoral Commission (@ElectoralCommUK) October 8, 2019

He said: “The May elections illustrate that delays in government action, which are needed to properly update our electoral laws, now pose significant risks to voter trust and confidence.”

Reacting to the report, the cabinet office said it will “carefully consider” the points raised and “respond fully in due course”.

In determining why some EU citizens in the UK were left unable to vote, the commission said it looked at evidence from various sources – including 618 formal complaints and 149 calls it received about the issue.

The report said the “most frequently cited concern” was that citizens of other EU member states living in the UK were unaware of the need to complete an additional declaration, as well as an application form, to register to vote.

Others said they were not given enough time to submit their declaration before the 7 May deadline, the report said.

While the commission was unable to “conclusively verify” how many people were affected, it said 1.7 million EU citizens who previously registered to vote did not submit an additional declaration in time to be registered for the 2019 European elections.

“Some of these people may have wanted to vote in the UK but were not able to submit the declaration in time before the deadline, although we have no data that allows us to assess how many were in this position,” the report said.

About 450,000 EU citizens were registered to vote in the May elections after submitting a declaration in time, the report said.

The commission said difficulties were “exacerbated” by the government not confirming its position on the election proceedings until “very late” in the lead-up to the May European elections.

This meant that electoral registration officers (EROs) had not sent declaration forms to EU citizens in the months before the election, as would usually have been the case.

The commission said that following the 2014 European parliamentary elections, it recommended a change in legislation to ensure EU citizens living in the UK did not need to complete more than one electoral registration form.

But it said the government did not change the law ahead of the 2019 elections.

The cabinet office said after the 2016 referendum the government did not bring forward changes around voting in European parliamentary elections, as the legislation to leave the EU meant there was no future poll planned in the UK.

The report said British overseas electors had also contacted the commission to say they were unable to return postal votes in time to be counted.

The commission said it will continue to urge the government “to consider new approaches” to improving access to the voting process for overseas voters.

“This could include voting at embassies and consulates, or the ability to download and print postal ballot papers,” the commission said.

The European parliamentary elections took place in the UK on 23 May, with voters choosing 73 MEPs in 12 electoral regions.

The report said 17.3 million votes were included in the count, representing an overall turnout of 37.2%.

A cabinet office spokesperson said: “The government put in place all the legislative and funding elements to enable Returning Officers to make their preparations for the polls on May 23.”

The cabinet office said the planning and running of the polls is the responsibility for Returning Officers (ROs), which are independent of the government.