A devout Sikh is suing the bank in London where he worked for more than £50,000 after colleagues allegedly made fun of his turban and asked him whether it “flashed red in an emergency”.

Harminder Dhanota, 42, claims that workmates would dislodge his turban and put a sticky note saying “sign here” on the back without his knowledge.

Mr Dhanota told a tribunal that Jack Tanna, his boss, had insulted his religion by showing him pornographic images on a mobile phone. Mr Dhanota, of Chadwell Heath, Essex, who is married with three children, said that Mr Tanna also offended him by asking him whether he was having sex with female colleagues.

He additionally alleged that Mr Tanna would punch his arm, twist his fingers and whack him on the hand with a ruler, making him cry out in pain.

Mr Dhanota, an IT manager, worked at the Mayfair office of Samba Financial Services, a Saudi Arabia-based bank. He is suing the bank for race and religious discrimination, sexual harassment and victimisation, seeking £56,825 for loss of earnings and injury to feelings.

His solicitor, Jay Joshi, commenting on his client’s allegations, said: “It is both shocking and ironic that such an ethnically diverse bank appears to condone such outrageous acts of bullying, harassment and discrimination.”

Mr Dhanota, who is British and of Indian origin, told the Central London Employment Tribunal: “I have always taken pride in my religion and culture and find it upsetting and distressing when people mock, ridicule or disrespect my personal beliefs.”

He said that in January 2012, he “politely reminded” Mr Tanna he was a Sikh and reported him in confidence to the Human Resources department.

Mr Dhanota alleged that his objections only spurred Mr Tanna on to humiliate him further in front of colleagues.

“At times, the physical assaults would be so aggressive as to cause my turban to loosen, which was the cause of significant distress to me,” he said.

In October 2012, Prakash Kale, another manager, allegedly asked Mr Dhanota: “Will your turban flash red in the event of an emergency?”

Mr Dhanota says that after he began to complain vociferously about his mistreatment, he was sacked from his £37,500-a-year job on claims of poor performance.

Samba Financial Group strongly denies all Mr Dhanota’s allegations and is vigorously contesting his claim.