Fewer than one in six wrongly accused subpostmasters have been sent letters confirming their convictions have been quashed, the Conservatives have said.

More than 700 subpostmasters were prosecuted by the Post Office and given criminal convictions between 1999 and 2015, as Fujitsu’s faulty Horizon IT system made it appear as though money was missing at their branches.

Shadow business minister Jerome Mayhew accused the Government of “exacerbating” the victims’ trauma by “sitting on the letters”, while Tory former minister David Davis urged the Government to send them out “quickly”.

Business Secretary Jonathan Reynolds admitted that progress on sending the letters out is “not fast enough”, but assured MPs it is a priority.

On Thursday, Mr Mayhew said: “When dealing with the Post Office Horizon scandal, does the minster understand that, by sitting on the letters informing Horizon victims that their convictions have been quashed, the department is exacerbating the trauma of this terrible injustice?

“After two months in office, I understand that fewer than one in six letters have been sent, so when is the minister planning to get a grip on this situation?”

During Business and Trade questions in the Commons, Mr Reynolds replied: “We have been in office two months and already set up the Horizon Convictions Redress Scheme.

“The issue with the letters is a Ministry of Justice issue with their database.

“We have not sat upon anything – we have moved at pace to give people the compensation they deserve, will continue to do so, continue to work with the Opposition front bench to deliver what we all want to see.”

Tory former minister Mr Davis said: “I’m sorry to say to the Secretary of State, saying it’s another department is what we’ve heard too many times.

“It’s his job to make this happen – can he please do so quickly?”

Mr Reynolds replied: “I’m not passing the buck to anyone, I’m simply saying it is the Ministry of Justice rather than myself that send those letters out.

“As of the 30th of August, 130 letters have been sent out, quashing more than 370 convictions. I think that is real progress since the election. It’s not fast enough for me, we’ll continue to push that and continue to do that.

“We are also working very closely with the Northern Irish and the Scottish administrations because of the devolved nature of justice, as he would expect.

“But I can assure him this was a priority for me in opposition, it will continue to be a priority for me in Government.”