Conservative Lucy Allan called for the Post Office and computer giant Fujitsu to be held to account over the Horizon computer scandal, which saw her constituent Tracy Felstead jailed for six months in 2001 after being convicted of stealing £11,500.
Miss Felstead, of Bournside Close on Telford's Brookside estate, is one of 44 former post office workers, mostly former sub-postmasters, whose convictions are now set to be overturned after the Post Office said it would not be contesting their appeals.
They say a glitch with the Post Office's controversial Horizon database caused shortfalls in their accounts, leading them to be accused of theft and false accounting.
The Horizon system, developed by computer giant Fujitsu, recorded all transactions carried out at branches. But hundreds of sub-postmasters and post-office staff complained that glitches were causing huge discrepancies.
Last year the Post Office agreed to a £57.75 million out-of-court settlement with 555 former post-office workers who took out a group litigation against it, saying they had been wrongly blamed. Mr Justice Fraser, who oversaw the hearing, ruled that the Horizon system was likely to have caused errors in the accounts. It later emerged that the majority of the pay-out would go on legal fees.
As well as miss Felstead, those affected also included Rubbina Shaheen, 55, who kept Greenfields Post Office in Shrewsbury, who was jailed for 12 months in 2010 over an alleged £40,000 shortfall in the accounts; Tahir Mahmood, who kept Selly Oak Post Office in Birmingham, jailed for nine months in 2005 for false accounting; and former West Bromwich postmistress Neelam Hussain, jailed for 21 months in 2011.
Miss Felstead, now 39, was jailed for six months in 2001 after being found guilty of stealing £11,500 from a post office branch in London.
Ms Allan said that Miss Felstead, and all those affected, had been badly let down by the Post Office, Fujitsu, the civil service, and ministers from all political parties over the past 20 years.
She told MPs: "Last week, the Post Office finally conceded defeat in the long-running battle between David and Goliath.
"How did a respectable organisation such as the Post Office, a major software company such as for Fujitsu, the great and the good in the civil service, and ministers from all parties fall prey to groupthink on such a grand scale, so that, despite this computer error occurring across the country, it was assumed that the only possible explanation was that all sub-postmasters affected were dishonest?"
She asked business minister Paul Scully what action would be taken to ensure the Post Office and Fujitsu were properly held to account.
She added: "Will he commit to determining who knew what and when during this shameful saga?"
Mr Scully said he hoped the inquiry, led by retired judge Sir Wyn Williams, would seek evidence in addition to the findings of Judge Fraser, by speaking to both the Post Office and Fujitsu, which had agreed to comply fully.
"My honourable friend is absolutely right that we need to get to the bottom of who knew what and when," he said.
"I also hope that sub-postmasters will, through conversation with Sir Wyn Williams, agree to get involved so that they can share their evidence and stories and so that we can get to the bottom of this, exactly as my honourable friend says."