Labour’s Pat McFadden has said he wishes he had asked more questions about the Post Office when he was a minister after the IT scandal emerged.
Mr McFadden was the minister in charge of postal affairs from 2007 for around three years.
The shadow minister recently claimed he could not recall the scandal being raised with him during that time.
However, he told the BBC that he had gone back and checked, admitting: “It did cross my desk.”
“Several MPs asked parliamentary questions or wrote letters,” he told the Sunday with Laura Kuenssberg programme.
Hundreds of sub-postmasters and postmistresses were prosecuted by the Post Office based on Fujitsu’s Horizon IT system – first installed in 1999 – which made it appear that money was missing from branches.
It is widely regarded as one of biggest miscarriages of justice in British legal history.
A number of former ministers with responsibility for the Post Office have faced questions about what they knew and when about the prosecution of branch managers based on faulty evidence from the computer system. The Post Office, which is owned by the government, denied for years that Horizon was at fault.
Mr McFadden is due to give evidence to a public inquiry into the Post Office scandal later this year.
Now shadow chancellor of the Duchy of Lancaster, Mr McFadden said that after looking at papers from 14 years ago, he was struck by “just how emphatic the Post Office was about this”.
He said: “Each time an MP raised a question about this, the reply would come back from the Post Office that they thought the system was robust, they had no evidence to suggest there was anything wrong with Horizon.”
Asked if he wished now that he had asked more questions at the time, he said: “Of course I do given what happened and the human tragedy of this was awful.”
In December 2009, Mr McFadden wrote in response to a letter from then-Conservative MP James Arbuthnot, a long-standing campaigner on the issue, that it was a matter for the Post Office, not the government, and Post Office had told him “there is nothing to indicate that there are any problems with the Horizon system”.
The following year he told Parliament that “issues relating to the Horizon system are operational matters for Post Office Ltd., which investigates all concerns raised by sub-postmasters about Horizon”.
On Sunday, he said that “two problems came together”.
“One was blind faith in the IT from the Post Office and the other was a culture of prosecutions of their own sub-postmasters,” he said.
Former Post Office ministers Sir Ed Davey and Jo Swinson of the Liberal Democrats and former Conservative minister Margot James have also been asked to appear in front of the public inquiry.
Sir Ed, who now leads the Lib Dems, has also said he regrets not asking “tougher questions” of Post Office managers when he was a minister, claiming he was “deeply misled”.
Alan Bates, who founded the Justice For Sub-postmasters Alliance and led the legal fight for justice, told BBC Radio 4’s Broadcasting House that victims of the scandals were still waiting for the compensation they are due.
“I don’t know why government cannot get the money out to these people, it just seems to be tied up in a bureaucratic nightmare,” he said.
“Everyone agrees the money is there but it’s just not happening and it needs to happen now.”