The Electoral Commission has been asked to permit late postal votes for the European parliament elections to be counted as reports continue of many British nationals living abroad receiving their ballot papers too late to return on time.

A group of 10 MEPs has written to the regulator to say that it should consider any postal vote that arrives by Sunday when the polls close across Europe. “We cannot permit lousy disenfranchisement like this,” said the Liberal Democrat MEP Catherine Bearder, who wrote the letter to the commission.

“This has left people’s voices silenced and is an affront to our democracy,” said the letter, also signed by Labour MEPs Seb Dance, Claude Moraes, Richard Corbett, and Jude Kirton-Darling, Change UK MEP Richard Ashworth, Green party MEP Molly Scott Cato, Plaid Cymru MEP Jill Evans and Scottish National party MEP Alyn Smith.

Catherine Bearder 🔶 (@catherinemep) I have authored a cross-party letter to the Electoral Commission on behalf of those UK citizens abroad who couldn’t vote because their postal vote never arrived. Similar letter for EU27 citizens being sent by @Claude_Moraes. We cannot permit lousy disenfranchisement like this. pic.twitter.com/2wG2rZHPf1

Voters in Australia, Canada and Japan have said they only received their paperwork on Monday, making it impossible to send a return postal vote in time for the deadline on Thursday.

Simon Payne and his wife, who live in Sydney, said they received their ballot paper on Wednesday, less than a day before the election.

The European election is being held over four days with just two countries holding their ballots on Thursday. The majority of member states hold theirs on Sunday.

In their letter to the Electoral Commission’s boss, Bob Posner, the MEPs said: “We would like to request that you allow all postal votes received before the count on Sunday to be considered valid given that it is still within the election period”.

The Electoral Commission said that by law votes had to be received by 10pm on Thursday and any extension would require a change to the law.

The MEPs’ letter comes as reports also continue of EU citizens living in the UK, including the Europe director of Amnesty International, being denied their right to vote in the election.

Gauri van Gulik said she was told by officials she could vote in her native country when she arrived at a polling station in north London. “I was denied my right to vote tonight in #Haringey, London. I was on the list but had a G next to my name. I was told “vote in The Netherlands”. What is happening in this country?” she tweeted.

As experts said the government could face legal action, more than 700 emails have been sent to the Guardian reporting missed votes.

Angry EU citizens, who said they would not be silenced, have complained to the Electoral Commission and councils across the country in an effort to get redress.

Timeline EU elections Show Hide European elections – what happens next

7am Polls opened on voting for the European elections across the UK and the Netherlands. Broadcasters now need to be very careful about reporting political news, sticking only to the blandest statements about the fact the elections are happening. 10pm Polls close. There will be no exit poll but some of the parties will have a bit of intelligence about how well or badly they have done, based on whether their supporters have been motivated to vote. Recess begins, meaning MPs are officially on a break from Westminster until 4 June – which usually limits their ability to plot as they disperse around the country. Morning: This is the most likely point for the prime minister to make a statement about her future, under pressure from her cabinet, backbenchers and the grassroots. Afternoon: If no statement is forthcoming, the 1922 Committee will open an envelope containing the results of a secret ballot on whether to allow another motion of no confidence in the prime minister. This is highly likely to lead to a defeat for May, making it probable that she will opt to set out a timetable for her departure at a time of her choosing. It is polling day in Ireland and the Czech Republic. Polling is continuing in Malta, Latvia and Slovakia so the results of the UK elections still cannot be revealed. All other EU countries have their polling days. 10pm: The votes can be published from now on and the first Europe-wide projection will be available soon after this time. 10.30-11pm: North East, South West, Yorkshire and the Humber declarations (based on 2014). 11.30pm Most Scottish results declared (based on 2014). Midnight: London, East of England, North West, Wales, West Midlands declarations (based on 2014). 12.30am East Midlands declaration (based on 2014). 2am: Most regions will have declared their results by now, so it will be pretty clear how the parties have done. Polls conducted in recent weeks have suggested the Conservatives are set for a dire showing, with Labour also underperforming. The Brexit party is expected to win and the Liberal Democrats and Greens to enjoy a surge in support. 2.30am South East declaration (based on 2014). Early morning: If May has set out her plans to resign by now, the Conservative leadership candidates are likely to be quick out of the blocks giving their opinions on the elections and setting out how they will turn their party’s fortunes around. Northern Ireland declaration will be finalised (uses a different system to the rest of the UK).

Many expressed anger that their name was on the register but had been crossed out, marked ineligible to vote, even though they had returned the paperwork to notify their local councils that they would be exercising their right to vote in the UK and not their country of birth.

There were also reports of confusion among officials. One clerk emailed to say he “saw first hand the lack of guidance regarding EU nationals’ voting rights” in a Cambridge polling station.

When EU nationals protested that they had completed the correct paperwork, there was no direction on what to do.

“The presiding officer was not clear on what to say,” the clerk said. The chief executive of the council visited the station and was vague on how to proceed. “It was a bit of a shambles,” said the official.

Play Video 2:25 'Our voice has been denied': German citizens in UK told they cannot vote – video

Many of the EU citizens spoke of their devastation at being turned away from polling stations, despite correctly returning the form to notify the council they would be voting in the UK.

One voter in London said she had returned both forms “well in advance” but was still turned away.

Diana Miranda, a Portuguese national said: “They gave me a card with the contact of the electoral registration office. I called and was told I didn’t send this second form and that I couldn’t vote in the election. I said I sent this second form but they just told me again that they didn’t get anything and I couldn’t vote.”

She said she felt it was was “absolutely disgusting that my voice and citizenship will be completely ignored”.

“I felt very sad, frustrated and even furious when I was not allowed to vote. This is a basic human right. I should have voted and I was turned away because of a two-tier administrative system that seems to treat citizens differently. It is discriminatory and it made me feel that I am not a full citizen.”

The Guardian received around 700 emails from both UK citizens abroad and EU citizens in the UK complaining about being denied the vote.

Several people have already filed complaints to the Electoral Commission on the grounds that the denial was a breach of article 9 (1) of directive 93/109/EC, which states: “Member states shall take the necessary measures to enable a community voter who has expressed the wish for such to be entered on the electoral roll sufficiently in advance of polling day.”

On Thursday the Electoral Commission said it recognised the frustration of voters but said the “very short notice” from the government about participation in the elections may have been part of the problem.

It also pledged to review the whole process in a post-poll report.

The European commission, the watchdog of EU law, said on Friday it would carry out a report into “the conduct of the elections in all member states and also the lessons drawn”, which is the standard process after the vote.

A commission spokeswoman said the organisation of the elections was down to member states.

“Of course it is always a concern to us whenever citizens cannot exercise their right to vote, that is accorded to them under the EU treaties, but again, it is foremost the responsibility of the national authorities to ensure that all EU citizens can exercise their voting rights.”

The commission is likely to present EU leaders with an early version of its report on election conduct in June, but the final version will not be published until the autumn.

The European parliament’s Brexit coordinator, Guy Verhofstadt, described reports as “worrying” and joined calls for an investigation. “The scale of this apparent problem needs to be investigated,” he said.