The government has yet to give formal notice of the poll, with the deadline next Friday, but this week agreed to pay for initial preparations
The prospect of Britain holding European elections would have been unthinkable just weeks ago but with the Brexit timetable now uncertain, the country is reluctantly planning for a possible campaign.
Village halls and schools across the country are being booked as polling centres, and orders placed with specialist stationers for tens of millions of ballots in case the May 23 vote goes ahead.
The government has yet to give formal notice of the poll, with the deadline next Friday, but this week agreed to pay for initial preparations.
And after Prime Minister Theresa May admitted she would
seek to again delay Brexit, amid continuing deadlock over her plan to leave, officials believe such notice is inevitable.
"If we were to still be a member of the EU, which is not our government's intention, but if we were, we would need to have European Parliament elections," Brexit Secretary Steve Barclay told MPs on Thursday.
Yet both the ruling Conservatives and the main opposition Labour Party are keeping quiet about any campaign plans, wary of how voters might respond.
May has previously said it would be "unacceptable" to ask Britons to take part in the elections three years after they voted to leave the European Union.
Her spokesman emphasised that once called, Britain could still cancel the polls up until May 22 if it has secured a deal to leave the EU by then.
This would cause anger in Brussels, not least because 27 of Britain's 73 MEPs have already been reallocated to other countries.
And it leaves Conservative candidates in the unenviable position of asking voters to back them in an election they themselves do not want, and still may not happen.
"That is not a conversation I relish having on the doorsteps of my constituency," said the party's leader in the European Parliament, Ashley Fox.
He said polls predicted voters would punish the Tories for betraying them on Brexit, with the best prediction suggesting it would lose half its 20 MEPs.
"It could be worse if our members decide they do not want to spend their evenings and weekends promoting a zombie election," he wrote on the ConservativeHome website.
Election officials, who would normally have begun planning for the European polls before Christmas, are now under intense pressure.
After pressing the government for weeks, ministers finally confirmed on Monday they would reimburse costs of preparations that were strictly necessary.
The process of booking venues and ordering stationery is now under way -- a mammoth task.
At the last European elections in 2014, they sent out 7.2 million postal votes, printed 46.5 million poll cards and had 39,000 polling stations.
Letters must also be sent out to more than three million EU citizens living in Britain to ask if they want to vote here or in their home country.
Laura Lock, deputy chief executive of the Association of Electoral Administrators, told AFP her members would do what was necessary, but that it would require a "superhuman effort".
IF UK is no longer part of EU at time of European Parliament elections in May, Italian citizens resident in UK won't be able to vote in those polls— Manuela Saragosa (@ManuelaBBC) April 4, 2019
The Conservative Party has so far refused to confirm what it is doing to select or field candidates for the elections, while Labour says only that it is "making contingency plans".
But smaller parties sense an opportunity.
The Scottish National Party (SNP) which wants to reverse the whole Brexit process, said it would contest any election "very vigorously".
The newly formed Independent Group, made up of pro-European former Conservative and Labour MPs, last week applied to the election authorities to be allowed to take part.
And Nigel Farage, a lead campaigner in the 2016 EU referendum, has said he would stand for his new Brexit party.
He condemned May's delay as the latest "Brexit betrayal" and said: "It is now clear we will have to fight our political classes again. I'm up for it."
European elections in Britain are typically marked by poor turnout, but Lock acknowledged Brexit could change this.
"People are planning for a higher turnout," she said.