Established to settle maintenance for children of separated parents, it aimed to ensure that absent parents were held financially responsible for their children.

It replaced the court system which was finding problems dealing with the increasing amount of cases it was facing.

But the complicated formula needed to work out payments has led to mistakes and delay, causing much misery and anger.

In some cases, absent parents have been overcharged, but in others - such as that of self-employed people - as many as 80% have avoided paying all the money they should because of loopholes in the system.

Many have avoided assessment and 30% of those assessed refuse to pay anything at all.

Cases which have attracted attention include that of unemployed Andy Burn from Tyneside, who has fathered nine children by nine women in 15 years.

He plays no part in their upbringing and the CSA can only claim �5 a week from his benefits.

And that of factory worker Keith Richard who was "over-charged" �1,450.

After complaining, he was told it would be paid back at the rate of �1.49 a week over 18 years.

Three-year programme

In her first annual report on the agency last September, independent case examiner Anne Parker called for a three-year confidence-building programme to shift "a defensive culture into a much more open one".

She said her watchdog had received more than 1,000 complaints about the agency in its first year.

She said that some customers had suffered "acute" financial losses as a result of maladministration.

But she praised staff for their even-handed approach to casework.

Fathers have been particularly vociferous in their opposition to the CSA.

The campaign group Familes Need Fathers says the agency is a failure and promotes "the prevailing social prejudice that fathers are irresponsible, feckless, and only relevant to the lives of their children in financial terms".

It says the Child Support Act, which the agency bases its work on, unfairly discriminates against unmarried fathers, requiring them to provide financial support when they have no other legal status with their child.

It wants fathers to be given more rights over contact with their children.

Its chairman Jim Parton said: "Fathers have to go to court and face a real uphill battle to get a contact order enforced."

But mothers are worried any changes over contact could promote domestic violence.

The Single Mothers' Self-Defence Group says many women who do not co-operate with the CSA are afraid that, if they do, they will be required to have more contact with men who may have abused them.

But the government argues that part of the reason single parents on Income Support do not work with the CSA is because they get no extra money if maintenance is paid.

It is proposing to remedy that by offering a �10 a week incentive.

Civil service

Civil servants have been in the frontline for any anti-CSA flak.

Last August, the Public Commercial Services Union announced that more than 1,200 staff - mostly those dealing directly with parents - had left the CSA in the first five months of the year.

It blamed poor pay, constant pressure and low morale.

The CSA said it shared concerns about staff leaving and had taken action to remedy the situation.

CSA workers are in the frontline for anti-agency feeling

Reforms have been introduced to improve the situation and life morale.

They include more use of telephone work so customers can be dealt with more swiftly, extending customer helpline opening hours and to deal with customers more quickly, better guidance for staff on how to deal with complaints.

Paul, a CSA worker who deals directly with the public, says that telling people outside work of his job sometimes "goes down like lead balloon".

"No-one really has a problem with the general principles of the CSA, but the ins and outs of each individual case makes it more awkward."

He says some customers get angry or distressed.

"You see people who are desperate for help, people who think you are the last person on earth they want to see and gentlemen in tears. It is very, very difficult.

"You have to use lots of understanding."

One line manager says staff need counselling training since they are often very young and unfamiliar with the kinds of problems customers are facing.

"I can find staff in tears after calls if they have been dealing with a distraught person on the phone.

"They need support. A lot of staff take it personally."

She added that most staff received a lot of support from their colleagues.

"You are dealing with two of the most difficult areas of people's lives: money and relationships," said Paul.

"And at a point when they are the least emotionally able to deal with them themselves because they have just broken up with someone."