Swiss cantons which used electronic vote-counting machines in last Sunday's ballot on the asylum issue are being ordered to do a recount - by hand.
The definitive, official result of the vote on tightening the country's asylum laws is not now expected before February.
Alexander Trechsel, political analyst
"The vote recount must be respected. In a democracy it must be possible to recount the ballots."
The asylum proposal, submitted by the rightwing People's Party, was rejected by a majority of just 3,422 votes.
But on Tuesday the federal authorities cast doubt on the result by ordering a partial recount.
The move follows revelations that around one-third of cantons used electronic counting methods without official authorisation.
In a letter to cantons the Federal Chancellery said all votes counted by electronic means alone would have to be recounted by hand.
The process is expected to take months, but political analyst Alexander Trechsel said the recount was necessary, even if it called to mind the electoral chaos in Florida during the last United States presidential election.
"The [US] electoral process was paralysed for months," Trechsel told swissinfo. We would prefer to avoid all that in Switzerland, but the vote recount must be respected. In a democracy it must be possible to recount the ballots."
Annemarie Huber-Hotz, head of the Chancellery, said there was no reason to fear that the use of scales or counting machines had led to inaccurate results.
The problem, according to Trechsel, was that the cantons "had not respected the law".
"Article 84 of the law on political rights requires that in federal voting the counting is done by hand."
Huber-Hotz said that in the event of a complaint being made, it would be difficult for cantons to justify their use of non-approved counting methods.
She added that a recount was necessary to dispel doubts among the Swiss about the correctness of the procedure used and the accuracy of the result.
"When the result is so close, we can't afford to let doubts persist about its reliability," Hotz's spokesman, Hansruedi Moser, told swissinfo.
The Federal Chancellery said only one canton - Geneva - had received the authorisation required for the use of electronic vote-counting machines. But nine other cantons admitted using counting machines.
"We were very surprised when we heard that these instruments are used by... several cantons and many communes... because nobody asked for permission until now," Moser said.
Just one canton - Bern - said it used scales to count its ballot papers.
Klaus Baumgartner, mayor of the city of Bern, said he had not sought permission to use the "extremely precise scales" when they were introduced in 1997, because he had not realised that this was necessary.
He said he would launch a recount "before any complaints were made". Other cantons were expected to follow suit.
Wide differences emerged on Wednesday between the methods used by the 26 cantons for counting the "yes" and "no" votes.
The Italian-speaking canton of Ticino said it only used electronic counting methods in the case of elections to the cantonal or federal parliaments:
"In Ticino, the ballots are always counted by hand in the polling stations, where 'yes' and 'no' votes are separated," said Gianpiero Gianella of the cantonal chancellery.
"In the case of political elections, the count is made electronically," Gianella told swissinfo.
The head of Aargau's election office, Urs Meier, said his canton had been using banknote counting machines for more than ten years.
"That is nothing new," Meier said. "The Federal Chancellery even knew about it."
Moser said the Federal Chancellery would be trying to standardise ballot-counting procedures to ensure there was no repeat of the problems surrounding the asylum vote count.
"It's the aim of the Federal Chancellery that we find a modus vivendi with the cantons by the time of the next federal vote on February 9, so that we can resolve this problem together."
swissinfo with agencies
The asylum proposal was rejected by a wafer-thin majority of some 3,422 out of 2,240,000 votes cast.
It was the closest vote on a people's initiative since 1891.
One-third of cantons used scales or counting machines without official authorisation.