Nacro, which works with offenders, said the Rehabilitation of Offenders Act 1974 is out of date and out of tune with the Government's desire to get more people off benefits and into work.
Nacro is to present MPs with its Change The Record report which sets out proposals to shorten the period of time before some convictions become spent and, therefore, do not have to be disclosed to employers.
Currently, offences resulting in fines have to be disclosed for five years, those resulting in prison sentences of up to six months have to be disclosed for seven years and sentences of up to two and a half years require disclosure for 10 years.
Nacro is proposing the period is dropped to one year for offences resulting in fines, and two new categories are created with prison terms of up to four years required to be disclosed for two years and above four years to be disclosed for four years.
The charity also proposes to ditch the current limit beyond which convictions can never be spent, which is currently a two-and-a-half year sentence.
Chief executive Paul McDowell said: "Around a quarter of the adult population has a criminal record. Outdated legislation and unlawful practices are preventing people from moving on with their lives and finding work.
"Research shows that getting reformed offenders into work can reduce re-offending by up to a half."
Nacro highlighted the case of one former offender, identified as Raymond, who got a three-year prison sentence for a post office robbery. Having recently completed a degree at Leeds University, he will never see his conviction "spent" under current legislation.
After committing the offence to fund a drug habit, he went on to become a successful salesman, eventually becoming an account manager.
But he did so without revealing his record to employers and when he came clean he found work almost impossible to obtain.
He said: At times I was tempted to turn back to my old life as no one seemed to accept the fact that I had rehabilitated and had plenty of skills to bring to the workplace."