A petition calling for the former Post Office chief executive, Paula Vennells, to lose her CBE over the Horizon scandal has attracted more than 1 million signatures.

Demands for the honours forfeiture committee to remove her CBE have re-emerged after ITV aired a drama about the scandal, which has been described as the most widespread miscarriage of justice in UK history. Vennells oversaw the organisation while it routinely denied there were problems with its Horizon IT system.

The petition, which is addressed to Sir Chris Wormald, the chair of the forfeiture committee, says: “Evidence has been produced that the Post Office engaged in a mass cover-up which led to the wrongful prosecution of 550 Post Office staff many of whom were subsequently jailed, bankrupted and in some cases, sadly took their own lives.

“Having been handed a CBE for services to the Post Office, and moved out into other senior positions in government and healthcare, it is only right that this award is now withdrawn through the process of forfeiture.”

Rishi Sunak confirmed that the justice secretary, Alex Chalk, was considering ways of helping to clear the names of convicted subpostmasters caught up in the scandal. Chalk and the postal minister, Kevin Hollinrake, are reportedly meeting on Monday to discuss measures the government could bring in.

Several prominent figures have said every person wrongly convicted in the scandal should be exonerated en masse by act of parliament in order to kickstart the process of compensating them.

“This is a mass problem which has got to be dealt with in a mass way, and I think that parliament has got to step in and say that Post Office convictions are not safe,” James Arbuthnot, who sits on the Horizon compensation advisory board, told media on Monday.

“We’ve seen the way that investigators behaved and they behaved in a way which was contrary to the rule of law. These convictions have got to be set aside.”

The former Conservative MP added: “One of the greatest problems is that there have been between 700 and 900 convictions and only 93 have been overturned. That is an awfully small … number.”

Many subpostmasters were accused of theft, fraud and false accounting based on data produced by the faulty IT system the Post Office imposed on them in the late 1990s. The Horizon software made it appear money was going missing from their branches and the Post Office relentlessly pursued people between 1999 and 2015; routinely denying there were problems with Horizon, despite knowing that from at least 2010 onwards there were faults in the centralised accounting software.

The scandal was uncovered after work by journalists at Private Eye and Computer Weekly, with several MPs also taking on the campaign for justice in recent years.

Prof Chris Hodges, who chairs the body overseeing efforts to compensate subpostmasters, said parliament must act unilaterally to clear those wrongly convicted. He told BBC Radio 4’s Today programme an act immediately overturning their convictions would mean the laborious process of assigning the compensation could start properly.

He dismissed concerns such action would compromise the independence of the judiciary, thereby setting an unacceptable precedent, saying there was no question of infringing on people’s rights. “The problem with both the [existing system for] overturning the convictions, and the compensation issue, is that individuals need to come forward,” he told Today.

Referring to the ITV drama, he said: “It’s been very vividly illustrated last week, that quite a number of people don’t want to have anything to do with lawyers or the state. They’re still traumatised and that is entirely understandable. They shouldn’t need to come forward. A civilised state should overturn these convictions and deliver compensation with people having to do as little as possible.”

One MP who sits on the Horizon compensation advisory board said prosecutions should follow. Kevan Jones told ITV’s Good Morning Britain: “Look at the evidence in court and the evidence which has come out at the public inquiry. [There are] umpteen charges that could be laid against a number of individuals. That has got to happen. People … want ultimately to know that people are going to be held to account.”

Read more:
Over one million sign petition to strip ex post office boss Vennells of CBE