A German “reader in law” at Soas University of London who is contesting a seat in the European parliamentary elections for the rightwing populist party Alternative für Deutschland (AfD) has been given the title of professor on the ballot paper, leading to accusations that his academic credentials have been exaggerated.

Dr Gunnar Beck is listed on Soas’s staff page as a reader in law who teaches courses on EU law and legal theory and undergraduate courses on legal methodology at the university. On the ballot paper for the European elections on 26 May, however, he was listed as “Prof Dr Gunnar Beck”.

A spokesperson for the German anti-immigration party told the Guardian it believed the title of “reader” at a British university to be equivalent to the rank of a professor in Germany.

Citing Oxford University’s definition of a “reader” as a “post at an intermediate level between that of full professor and associate professor”, the spokesperson said that translating the title into the German “professor”, “seemed and seems correct, because it was always clear that Dr Gunnar Beck works in Great Britain”.

However, the ministry for science in the state of North Rhine-Westphalia, where the ballot paper states Beck is based, has categorically rejected the claim that the two titles are equivalent.

“Irrespective of the weight of the English ‘reader’, carrying the title in the form ‘prof’ or even ‘professor’ is in this case out of the question,” the ministry said in response to a query from Deutschlandfunk radio.

Beck denies having exaggerated his academic credentials himself. In an email to the Guardian, he said: “I can’t imagine I ever used the prefix ‘Prof’ or ‘Prof Dr’ in writing, let alone in introducing myself, just as I practically never sign as ‘Dr’ or introduce myself as such. Others in Germany and possibly elsewhere must have taken it upon themselves to add those to my name, thinking this either appropriate in my case or customary in Britain too.”

Beck said he categorically denied filling in the form with anything other than his first name and surname.

According to a claim on his Wikipedia page, deleted on Saturday, Beck was “appointed professor of law at the University of Sussex in 2016”. But when approached by the Guardian a spokesperson for the university said it had not appointed the German academic as a professor.

“We can confirm that Gunnar Beck does not work, and has never worked, at the University of Sussex. In addition, he has never been appointed professor at the University of Sussex,” they said.

It is not known who included the information on the page or who deleted it.

Beck also introduced himself as a “professor” during his speech at a AfD party summit in Magdeburg last November.

Unauthorised use of an academic degree or an official title is a criminal offence in Germany according to paragraph 132a of the penal code.

The debate over Beck’s academic credentials was originally picked up by a post on the German legal blog verfassungsblog, in which the author Maximilian Steinbeis had pointed out that a factually incorrect ballot paper could potentially have an impact on the composition of the next European parliament and could therefore invite voters to legally contest the validity of the vote.

“In the strict sense of the law, the consequence would be that the European elections would be invalid throughout Germany and would have to be repeated,” Steinbeis wrote. “The EP [European parliament] and the entire EU would be paralysed for weeks or months.”

Recalling the ballot papers is not an option since they have already been printed, sent out and in some cases may have already been returned by voters.

As well as teaching law at British universities, Beck was a prolific commentator for British and German media on the debate over bailouts during the eurozone debt crisis, and more recently on the negotiations between Britain and the EU following the Brexit vote.

Before joining the AfD in spring 2014, Beck wrote two op-eds for the Guardian, arguing that the rescue fund for struggling eurozone countries violated EU law and would damage the German economy.

In an earlier statement Beck said: “I was and am opposed to the euro rescue policies of the German government which I believe to be unaffordable for the German population in the long run and to be socially divisive throughout the eurozone.”