The Government has already made some changes to the agency, set up to assess and collect maintenance from absent fathers, but critics want to see it scrapped.
The figures were given to Tony Wright, Labour MP for Cannock and Burntwood, by the CSA chief executive, Ros Hepplewhite, who said that in the year up to March the agency received 10,866 formal complaints. But only 45 per cent of these were dealt with in 10 days - the agency's target time.
Dr Wright said: 'It is simply not acceptable for a system to generate such a high volume of complaints and then fail to meet its own targets for handling them. This information strengthens the case for a complete review of the way the CSA is working.'