Gerhard Schroeder, the former German Chancellor, is being sued by his South Korean fiancée’s ex-husband for allegedly having an affair with her while she was still married.

South Korea remains a deeply conservative society where extramarital affairs were a criminal offence until 2015, with some offenders – both the straying spouse and the lover – receiving jail terms.

While no longer a criminal offence, affairs remain grounds for civil legal action.

Mr Schroeder, 74, chancellor from 1998 until losing to Angela Merkel in 2005, announced in January that he would marry Kim So-yeon, a South Korean translator 26 years his junior, after his fourth marriage fell apart.

Mr Schroeder’s colourful private life and multiple marriages previously earned him the nickname "Audi man", a reference to the German carmaker’s four-ring symbol.

Ms Kim and her husband divorced in November. Doris Schroeder Kopf, the former leader’s fourth wife, said last September in the process of divorcing him that the South Korean had played a part in the breakup.

Ms Kim was a translator for the former chancellorCredit:

The two started dating each other while both were still married, Ms Kim’s ex-husband claimed. He is suing Mr Schroeder for 100 million won (£68,000) in damages for "unbearable mental distress", Yonhap news agency said.

The suit had been filed in the Seoul Family Court, it said, without disclosing the husband’s name.

"The accused (Schroeder) continued extramarital affairs with Kim knowing she is a married woman, causing unbearable mental distress," the husband is quoted as saying in a court document.

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"Our marriage eventually fell apart, and the accused should be held responsible for his action," it said.

Mr Schroeder insisted in January that Ms Kim had nothing to do with the breakup of his fourth marriage.

Ms Kim is a Seoul representative of the Economic Development Agency of the German state of North Rhine-Westphalia and has worked as a Korean translator for Mr Schroeder.

The Social Democrat served as German chancellor from 1998 to 2005 and instituted labour market and welfare reforms which angered the left of his party.