Agree about the proportionality, but there does not need to a prosecution for HMRC to use its powers to require third parties to provide data relevant to the tax position of a person. See hereNo. Not without prosecuting you for evasion, first. In the first instance they might ask you to provide the basis for your breakdown, but the record keeping requirement is supposed to be proportional to size of claim/tax burden, etc.
http://www.hmrc.gov.uk/manuals/chmanual/CH23620.htm