Black Post Office workers who were falsely accused in the Horizon scandal were classified using a racial slur, according to documents obtained by campaigners.
More than 700 former Post Office staff were wrongly prosecuted for theft and false accounting in what has been described as "the most widespread miscarriage of justice in UK history".
Post Office prosecutors tasked with investigating sub-postmasters were asked to group suspects based on racial features.
The document, thought to have been published in 2008, asked investigators if the suspects were "N*****d Types" - a racist term from the colonial era of the 1800s that refers to people of African descent.
Other categories on the document include "Chinese/Japanese types" and "Dark Skinned European Types".
Seema Misra, who was pregnant with her second child when she was jailed after being wrongly convicted of stealing from the Post Office she ran in Surrey, said she was angry at the new revelations.
"Now I think, because they had a racist thing in their mind, my case could have been different if I wasn't Indian," she said.
"They might not have suspended me, they might not have taken the case, I don't know.
"We had to move. We lost everything, to be honest - we lost the business, we lost everything. We lost our dignity, lost our pride, everything."
The documents came to light through a Freedom of Information (FOI) request obtained by campaigner Eleanor Shaikh.
She is a supporter of the more than 700 branch managers who were prosecuted between 1999 and 2015 on theft, fraud and false accounting charges.
Responding to the FOI, a Post Office spokesperson described it as a "historic document" but said the organisation did not tolerate racism "in any shape or form" and condemned the "abhorrent" language.
They added: "We fully support investigations into Post Office's past wrong doings and believe the Horizon IT Inquiry will help ensure today's Post Office has the confidence of its postmasters and the communities it supports."
A statutory, independent inquiry began in 2022 to examine how the Horizon scandal happened.
The sub-postmasters were falsely accused of theft and false accounting after a computer system called Horizon was introduced by the Post Office in 1999 and incorrectly showed shortfalls on company accounts.
In 2000, the Post Office began taking legal action against sub-postmasters using Horizon data as evidence. By 2014, 736 had been criminally prosecuted.
Some ended up in jail, others became bankrupt trying to repay money they did not owe, and a few even took their own lives before their names could be cleared.
However, in December 2019, a High Court judge ruled the system contained a number of "bugs, errors and defects" and there was a "material risk" that shortfalls in Post Office branch accounts were in fact caused by it.
Many sub-postmasters have had criminal convictions overturned.