The independent watchdog - set up to investigate complaints against the agency - has said the CSA's failure to improve its performance was "beginning to be a worry".

Independent case examiner (ICE) Anne Parker insisted she wanted to see "real measurable changes" in the CSA's performance during the next three years.

She was speaking at the launch of the first annual report on the CSA - set up to track down absent parents and extract maintenance payments - by the independent case examiner.

Shake-up

Her criticism came despite an extensive shake-up of the CSA, designed to improve its efficiency, unveiled by the UK Government in July.

Under the government's plans, the agency will introduce a much simplified formula for assessing the liability of absent parents to pay child maintenance.

Ms Parker said: "It is a very difficult job and if I were doing it, would I guarantee to get it right all the time? It is an error-prone system."

An improvement in performance would not happen overnight, she conceded.

This was why she underlined the need for the three-year confidence-building programme to shift "a defensive culture into a much more open one".

Ms Parker was setting out the findings of the report which showed that her watchdog organisation received over 1,000 complaints in its first year and cleared 820 of them.

She fully or partially upheld the client's complaint in 93% of the 150 cases where a lengthy investigation was carried out.

But the examiner praised CSA staff in the report for their commitment and clear understanding of the need for an even-handed approach to their work.

'Frustrated'

However, Ms Parker added that CSA customers had been "frustrated" and "sometimes grossly inconvenienced" and, in some cases, had suffered "acute" financial losses due to maladministration by the agency.

The Deputy Chief Executive of the CSA, Mike Isaac, admitted that the examiner had "rightly identified areas where the agency's procedures and performance have merited criticism.

He said that Ms Parker had also recognised the Agency's commitment to improving performance across the board.

Improvements

In the year covered by the examiner's report, many important initiatives and changes had been introduced to target the causes of complaints and ensure better customer service, Mr Isaac added.

These changes included: