A Swiss court has sentenced four members of the UK’s richest family to prison sentences ranging from four to four-and-a-half years.

Prakash and Kamal Hinduja as well as son Ajay and his wife Namrata were found guilty of exploitation – usury in the Swiss penal code – and illegal employment.

But they were acquitted on the more serious charge of human trafficking.

Workers who were brought over from India alleged the family paid them as little as £7 ($8) to work 18-hour days, less than a tenth of the amount required under Swiss law.

They also claimed the family – whose fortune is estimated at around £37bn – rarely allowed them to leave the house, in Geneva’s wealthy neighbourhood of Cologny.

During the trial, prosecutors alleged the family spent more on their dog than on their servants.

The elder Hindujas, both over 70, have not been attending court proceedings, pleading ill health. Ajay and Namrata had been present, but they were not in court to hear the verdict.

The Geneva prosecutor has called for their immediate detention.

It is not the first time that Geneva, a hub for international organisations as well as the world’s wealthy, has been in the spotlight over the alleged mistreatment of servants.

Last year, four domestic workers from the Philippines launched a case against one of Geneva’s diplomatic missions to the United Nations, claiming they had not been paid for years.

The Hinduja family own Hinduja Group, a multinational group with interests in oil, gas, and banking. The family also own Raffles hotel in London.