After a number of lapsed deadlines to provide the report, that was claimed to run to 80 pages, the Business and Trade Committee revealed it had been told to expect a 12-page document.

This was understood by the Post Office to be the 'HR (human resources) report' at the centre of a row between the firm's former chair Henry Staunton and Mr Read.

The Post Office said the longer document was believed to relate to another individual.

The existence of the conduct report came as a bombshell last week.

It had been thought that Mr Staunton, sacked earlier this year by business secretary Kemi Badenoch, had been subject to investigation.

But at a committee hearing last week, Mr Staunton said he was only mentioned in one paragraph and the report was "a big investigation into Nick".

The report was said to have been compiled by a former human resources (HR) director and whistle-blower and said Mr Read threatened to resign because he was unhappy with his pay and made accusations of bullying. According to a Sunday Times report, Mr Read sought a £1.1m pay package.

Mr Read has denied he made resignation threats.

On receipt of a letter from the Post Office to clarify its position on the report, the committee said: "The Post Office's senior independent director, Ben Tidswell, suggested that the document in question is most likely a 12-page whistleblowing 'Speak Up' report.

"He has agreed to provide this within the next 24 hours."

In his letter - published by the committee - Mr Tidswell wrote: "We greatly value your commitment to safeguarding data and individuals referred to in an external whistleblowing investigation, and your belief that it would be highly unlikely that the Committee would resolve to publish the documents that you have requested unless there was a public interest in doing so and, even then, only with proper redactions to protect the rights and interests of those individuals."

The row has overshadowed the fight for justice by former sub-postmasters who were front and centre of the committee's hearing.

Victims of the Post Office's faulty Horizon software have been seeking redress after hundreds were convicted of false accounting, theft and fraud and many more lost their businesses and were in financial and personal ruin after the Fujitsu-built accounting software wrongfully documented monetary shortfalls.

Read more:
Who is Henry Staunton, the City grandee who took on Kemi Badenoch?

After he was removed from his post, Mr Staunton said he had been told by the Department for Business and Trade to slow down the processing of compensation.

In documents exclusively obtained by Sky News, he called for the Post Office to be "removed completely" from the compensation process and for it to be put under the control of postmasters due to the "deep dysfunction" within the organisation.

It's understood the chair of the Business and Trade Committee, Labour MP Liam Byrne, requested the HR investigation be sent to the committee by last Thursday, and when the deadline passed, by Monday afternoon.