The Post Office dropped a wide-ranging review into the convictions of sub-postmasters over fears it would make “front page news”.

Paula Vennells, the former Post Office boss, had suggested in 2013 that convictions going back 10 years could be scrutinised.

But in an email revealed at the inquiry into the Horizon IT scandal on Thursday, ex-Post Office media chief, Mark Davies, told Ms Vennells that it would “fuel the story and turn it into something bigger than it is”.

Mr Vennells replied at the time that she would take her PR adviser’s “steer” but admitted at the inquiry such a review could have “avoided a lost decade” in terms of discovering miscarriages of justice.

On a second day of questions, Ms Vennells was grilled about a report by forensic accountants Second Sight which was published on 8 July, 2013 and flagged up bugs in the Horizon IT system.

The Post Office had previously insisted that Horizon – which is accountancy software used by sub-postmasters in their branches – was robust.

In an email to colleagues prior to the report’s publication, Ms Vennells made suggestions to address concerns of campaigners including Alan Bates and Lord Arbuthnot about the safety of previous Horizon convictions.

This included reviewing all convictions for false accounting stretching back up to 10 years “in the light of the Second Sight findings”.

Mr Davis said: “If we say publicly that we will look at past cases… we will open this up very significantly into front page news. In media terms it becomes mainstream, very high profile.”

Ms Vennells responded: “You were right to call this out, and I will take your steer, no issue.”

Lead counsel for the inquiry, Jason Beer KC, asked Ms Vennells asked if this meant that she took the advice of Mr Davis not to look back further into past cases.

Ms Vennells began to respond, saying “I really don’t remember it relating to the decision” prompting groans from the public gallery where former sub-postmasters and postmistresses were watching proceedings.

This sparked a rare intervention by Sir Wyn Williams, chairman of the inquiry, asking for calm.

Mr Beer said that had the idea been put into effect, it may have “avoided a lost decade” in terms of discovering miscarriages of justice.

“It may well have done,” conceded Ms Vennells.

Hundreds of sub-postmasters and postmistresses were convicted for offences including theft and false accounting on the strength of faulty Horizon data. Money was flagged as being missing from Post Office accounts, when in reality, it wasn’t.

From 1999 to 2015, there were 983 UK convictions – the majority of which were prosecuted by the Post Office itself, which is owned by the government.

A smaller number of cases were prosecuted by the Crown Prosecution Service.

Ms Vennells admitted on Wednesday that she did not know until 2012 that it was the Post Office and not external bodies that were prosecuting sub-postmasters.

She joined the firm in 2007 and was promoted to managing director three years later.

So far only 103 sub-postmasters have had their convictions overturned.

Sub-postmasters were required to repay the supposedly missing funds and many were still prosecuted. Some went to prison and many were ruined financially.

Ms Vennells said that Mr Davies was trying to “minimise misinterpretation and exaggeration in the media” due to the Post Office thinking at the time that there had only been a small number of possible problems with convictions.

Mr Beer said the idea of not looking back at past convictions because it could generate front page news was “a grossly improper perspective”, to which Ms Vennells replied: “Yes, it is.”

She added that she would “never” have taken the advice of just one colleague on this.

Speaking to the BBC in a break in the proceedings, former sub-postmaster Jo Hamilton said the decision not to go ahead with a review was “a deliberate missed opportunity”.

Former sub-postmaster Seema Misra, who was sent to prison while pregnant, added that she thought it was evidence of a “cover-up”.