Investigators probing alleged ‘false accounting’ in Post Office were asked to categorise suspects according to their racial backgrounds, a media report said.

Hundreds of sub-postmasters were wrongly subjected to investigation for ‘fraud’ based on information from the Horizon computer system which was later found to be faulty.

More than 700 branch managers were prosecuted between 1999 and 2015 and some of them were imprisoned in what is known as "the most widespread miscarriage of justice in UK history".

Several convictions have since been overturned.

The guidance for the investigation required the investigators to give sub-postmasters under suspicion a number based on their racial features, the BBC reported, citing internal documents.

The numbered categories on the document included 'Chinese/Japanese types', 'Dark Skinned European Types' and 'Negroid Types', the report said.

Adeep Sethi, whose parents were victims of the computer system installed in the Post Office branches they ran near Romford in Essex, said he was “not surprised” by the racist language used in the investigation.

"This was from a Freedom of Information request and not the Post Office coming out and saying 'we've messed up' - it was only because someone dug into it," Sethi told BBC Radio 4.

Post Office said it “does not tolerate racism in any shape or form.”

Its spokesperson said, “The language used in this historic document is completely abhorrent and condemned by today’s Post Office. We fully support investigations into Post Office’s past wrongdoings and believe the Horizon IT Inquiry will help ensure today’s Post Office has the confidence of its postmasters and the communities it supports.”