Lawyers who advised the Post Office on criminal conviction appeals urged the organisation to oppose mass exonerations last month, it has emerged.

Correspondence published by the Post Office last week revealed that Nick Vamos, partner and head of business crime at City firm Peters & Peters, wrote in response to reports that legislation may be used to overturn every one of the hundreds of Horizon-based convictions from the last 20 years.

Vamos, writing for and on behalf of his firm, said he had been ‘listening with growing concern’ to proposals for overturning convictions without going through the court processes and that the government risked doing so on a ‘false basis’ because it did not have all the relevant information.

Vamos continued: ‘In reality, it is highly likely that the vast majority of people who have not yet appealed were, in fact, guilty as charged and were safely convicted.

‘Unless this is made clear to the government, it risks making incredibly important and expensive decisions on a completely false premise. I am sure that this point has been or is being made to whoever is briefing [justice secretary] Alex Chalk, but I also know that points can be misunderstood or watered down by the time they reach a minister, and this is one point that cannot be made strongly enough.’

It is unclear why the Post Office opted to publish correspondence from its legal advisers now. The debate around legislation to overturn all convictions increased last week as the government ruled out taking the judiciary’s preferred option of relying on the courts to make decisions on appeals. The bill to clear all sub-postmasters will have a financial effect as those individuals would automatically be eligible for a minimum of £600,000 compensation.

The letter pointed out that many cases are still going through the Criminal Cases Review Commission and that more than 30 appeal applications had already been rejected based on ‘clear confessions and/or other corroborating evidence of guilt’.

The Post Office said the note, written within days of the ITV drama that catapulted the Post Office scandal to the top of the news agenda, was not solicited by the organisation and was sent to express the views of its author.

The Post Office’s explanatory note stated that the organisation had made no attempt to persuade the government against mass exonerations, despite the input of its legal counsel.

Peters & Peters was instructed in January 2020 to conduct a post-conviction disclosure exercise and to represent the organisation in every appeal against convictions in England and Wales. The firm has made no further comment publicly but points out that where the Post Office has opposed appeals, convictions have been upheld. The firm’s conduct of appeal proceedings and disclosure responses have been commended several times by judges handling proceedings.

The advice that people with sound convictions may be exonerated has also been reiterated by the government. Post Office minister Kevin Hollinrake, announcing legislation to clear all sub-postmasters with criminal convictions, accepted that workers who had stolen money could be exonerated as part of the group order.

In a statement to parliament last week, Hollinrake added: ‘The government accepts that this is a price worth paying in order to ensure that many innocent people are exonerated.’

As well as the advice from Peters & Peters, Post Office also published a letter sent last month to the justice secretary by its chief executive Nick Read.

In it, Read had said: ‘We make absolutely no value judgment about what you and your colleagues determine as the right course of action, but consider it essential for you to understand the very real and sensitive complexities presented each case.’