It is "staggering" that probation officers can spend as little as a quarter of their time dealing directly with offenders, MPs said today.
The Commons Justice Committee criticised the "tick-box, bean-counting culture" which has left staff tied up filling in paperwork rather than supervising and helping to rehabilitate criminals.
The MPs recommended that probation trusts should be given greater independence and said there was an "urgent need" for scarce resources to be focused on the front line.
Publishing a report into the role of the probation service in England and Wales, the committee called on the Ministry of Justice to commission an external review of the National Offender Management Service (Noms).
The MPs questioned whether Noms, which was established in 2004 and effectively merged the prison and probation services, was delivering good value for money, giving probation trusts the support and freedom they need, or co-ordinating the supervision of offenders in jail and the community.
They raised particular concerns about "micro-management" by Noms and the volume of form-filling probation staff must do to comply with the agency's targets.
The report said: "We accept that probation officers have to do a certain amount of work which does not involve dealing directly with offenders.
"However, it seems to us staggering that up to three quarters of officers' time might be spent on work which does not involve direct engagement with offenders.
"No-one would suggest that it would be acceptable for teachers (who also have to do preparatory work and maintain paperwork) to spend three quarters of their time not teaching.
"The value which really effective probation officers can add comes primarily from direct contact with offenders.
"While we do not want to impose a top-down, one-size-fits-all standard, it is imperative that Noms and individual trusts take steps to increase the proportion of their time that probation staff spend with offenders."
Justice Committee chairman Sir Alan Beith, a Liberal Democrat MP, said: "Probation is an essential part of the criminal justice system and at its best the probation service delivers community sentences which are tough, challenging offenders to change their offending lifestyles.
"The ability of probation professionals to undertake effective work directly with offenders has been hindered by a tick-box culture imposed by the National Offender Management Service which has focused predominantly on prisons and has micro-managed probation."
Harry Fletcher, assistant general secretary of probation service union Napo, added: "The report confirms that the National Offender Management Service has been a major problem from the start.
"Napo warned in 2004 that Noms would be a bureaucratic nightmare. It is scandalous that probation staff now spend 75% of their time on form-filling and responding to centrally driven emails."
Mr Fletcher went on: "The last 10 years has witnessed a massive rise in the constant Government monitoring of probation staff to the detriment of face-to-face contact with offenders.
"This does not enhance public protection but undermines it. This flawed historical trend must be reversed."
Probation and Prisons Minister Crispin Blunt said: "I heartily agree that the probation service needs to be freed up from unnecessary red tape in order to focus on reducing the appalling rates of reoffending.
"Half of the people we release from our jails are re-convicted within a year of getting out.
"That's why we're making changes to enable probation officers to use their judgment and discretion more widely. The culture of target-setting and box-ticking is over."
But shadow justice secretary Sadiq Khan MP claimed the Government was "taking a big gamble with public safety" by "cutting too far and too fast" in the prison and probation services.
He said: "It is irresponsible to shed thousands of front line staff from the probation service at the time they are expected to take on a greater role in working with offenders in communities.
"Tough community sentences can be used as effective punishment and to reform offenders, but if they are to work, they must be properly resourced and the public must have confidence in their ability to act as a punishment and a deterrent."
Speaking on the BBC Radio 4 Today programme, Justice Committee chairman Sir Alan Beith, a Liberal Democrat MP, said the value of a probation officer was "what he can do to turn an offender's life around, to make the offender think differently".
He said: "We had offenders in front of us who talked about how that relationship can work and how it needs to be a strong and assertive one - not just someone being friendly, but someone who's challenging them to think differently."
He added: "It was brought to us in evidence by frustrated probation officers who said that it was still a problem for them. I think it was micro-management, it was box-ticking, it was all the things we've come to associate with a target culture which really do need to be changed."
Sir Alan said Noms needed "completely restructuring" and there needed to be a move in the direction of "local commissioning of both prison and probation".
Justice Secretary Kenneth Clarke said he was "staggered" by the quarter figure.
He said: "We knew it was a problem and we've been addressing it. It goes back to a failed system of management where you pile targets and micro management and stipulate to people what they should do, which we've been getting rid of.
"I've already started addressing this. We've reduced the number of targets, we've streamlined the national standards, we've said that we're going to give probation officers back their professional discretion."