Information in relation to the allocated costs of Government contributions to child trust fund accounts, including forecasted costs to 2012-13, is contained in table 9 of the 2009 Statistical Report which can be viewed on HM Revenue and Customs' website:
http://www.hmrc.gov.uk/ctf/statistical-report-2009.pdf
For years prior to 2007-08 the allocated costs were set at £240 million per full year.