Divorced or separated parents who refuse to support their children will face tougher measures from next month when the Child Support Agency (CSA) is replaced. But for every father shirking his responsibilities, campaigners say there is an innocent parent mired in the bureaucracy of the controversial Government body. Simon Barrett reports.

When the CSA was set up in 1993, it was immediately beset by problems.

Two failing computer systems, inaccurate estimates, a failure to enforce payment and cases in which the wrong people were pursued.

The controversial brainchild of former prime minister Margaret Thatcher, the CSA is meant to calculate and collect maintenance from non-resident parents - usually fathers - and pass it on to the parents with care - usually mothers.

But the system works extremely poorly for many people.

One single mother, from Southwick, told The Argus she almost reached breaking point after the CSA overcharged her by almost £60,000.

The mother-of-three, who did not want to be named, was shocked to receive a bill for £73,000.

She split from her husband 12 years ago but she continued to care for her eldest son, then 14.

Her former husband cared for their other two children, and on weekends they took turns looking after all three.

But the CSA sent the mum a bill for £73,000 claiming that was what she owed her ex-husband in child support.

Overwhelmed by jargon and red tape she began to suffer depression and took four weeks unpaid leave from work.

It was only after persistent pressure that the agency wrote to her five months after the original bill, admitting it had miscalculated to the tune of £59,000. She said: "It took months of paperwork and the stress of waiting before they agreed I actually owed £14,387 - which is still ridiculous.

"But this was all 11 years ago, the kids have all grown up now and the youngest is 17.

"They are taking £353 out of my monthly wage, yet my exhusband is not seeing any of it.

"And they say I can't claim from him for caring for our eldest son for those years because it's too late - yet it's not too late for them to chase me.

"It's completely ridiculous. That is a lot of money and all they are doing is still hurting the kids.

"I can't afford to help my son go on holiday this year because I've got no money - so it is him that is suffering because of this nonsense."

About 18,500 parents in Sussex owe a total of £71.7 million in maintenance for their children - an average debt of £3,876.

Nationwide, one parent in three who should be paying maintenance is failing to do so.

The CSA uses everything from fines to bailiffs, court orders and the threat of prison to urge debtors to pay up.

Last year the Argus forced the CSA to review the case of John Ward, an emphysema sufferer from Bolney Road, Moulsecoomb, Brighton.

Mr Ward, who is registered disabled, was sent a letter demanding £9,419 in backdated maintenance payments for the period November 1996 to December 2006.

The letter said if he could not arrange payment within seven days, it would be passed to a debt collection agency.

The former bus driver told how he lived on £76 a week from part-time work and £70 a week incapacity benefit.

He said: "I'm one of thousands of people in this country being walked all over by the CSA. They are a law unto themselves."

This week The Argus was invited behind the scenes at the CSA's South East base in St Leonards.

Staff admitted they had a bad reputation but said they were were working hard to help children who are suffering because their parents' relationship has failed.

Principal legal enforcement officer Stuart Richards said the amount of money owed in Sussex was a shocking figure.

He said: "Much still needs to be done to collect money from the non-resident parents who refuse to pay and our enforcement powers have been strengthened to do this.

"We give the parents every option to pay but where they don't, we pursue that and do all we can to help them pay before registering a debt. We don't want to have to take this action.

We want it sorted as soon as possible. Our role is about making them aware."

Those debt-recovery powers open to the body will increase even further next month when the much-maligned CSA is replaced by the Child Maintenance and Enforcement Commission (C-MEC).

The power to take money from bank accounts without consent and without a court order, the power to freeze accounts, seize the proceeds of house sales, impose curfews, and confiscate passports and driving licences will all be available to the authority.

Yet some fear the changes will only increase the heartache - and lead to even greater confrontation and friction.

So what could happen in future to improve the system?

One Parent Families is a charity which wants Britain to follow other countries in having the state act as guarantor, making maintenance payments if the non-resident parent defaults and chasing up the money later.

A spokeswoman said: "What parents with the day-to-day care of a child need is a strong and effective service focused on collecting adequate levels of maintenance on a regular basis for their children.

"If C-MEC decides that nothing more can be done in a particular case, we think the parent with care should then get compensation, where they can show that the CSA bears some responsibility for the failure to recover the child maintenance owed."

Thousands of parents in Sussex will be hoping that, with the changes ahead, things can only get better.

Have you had dealings with the CSA? Was it good or bad? Share your experiences below.