Predictions of the results for the states of Saarland, Thuringia and Saxony appeared in ‘tweets’ on the microblogging site. They were all were within a percentage point of exit polls published an hour and a half later.

The news has raised concern that a similar leak in the general election – now less than a month away - could cause chaos by rendering the result invalid.

As in many countries, it is illegal in Germany to publish exit polls before the real polls have closed in case they influence how people vote (or whether they vote at all). However, political parties and the media often have confidential access to early results in order to prepare reports and speeches. Anyone breaking the rule faces a fine of up to €50,000.

German news site Der Spiegel reported that one of the Twitter accounts used to post the predictions belonged to Patrick Rudolph, leader of the CDU party in the town of Radebeul, Saxony. He told Der Spiegel he has no idea who posted the figures, and has now deleted the Twitter account - but not before the information had been widely read and repeated.

The results were posted at around 4.30pm, 90 minutes before the polls closed.

An election official in Saxony told Der Spiegel that legal action would be considered if it is determined that the predictions published on Twitter were based on survey results, and not just hearsay. This could also lead to the election result being declared invalid.

Official preliminary results show the CDU winning in all three states, with 34.5% in Saarland, 40.2% in Saxony and 31.2% in Thuringia.

Roderich Egeler, head of the federal electoral committee, said the early publication of exit polls in the general election would be the “worst case scenario”.