mps quiz aides over royal income senior officials at the two bodies generating private income for the queen and prince of wales are to be questioned by mps.  aides from the duchy of lancaster and duchy of cornwall will appear before the commons public accounts committee. it has been reported they could be questioned about prince charles  spending on camilla parker bowles. but bbc correspondent peter hunt said they are not responsible for how money is spent and may be unable to answer. duchy officials  who will appear before the committee on monday  are only responsible for generating money. the duchy of lancaster provides the queen s private income  while the duchy of cornwall provides prince charles  annual income. the duchy of cornwall is a 140 000-acre estate across 25 counties  and also includes residential properties  shops  offices  stocks and shares. it was set up in 1337 by king edward iii to provide income for successive heirs to the throne. it covers the cost of the prince s public and private life - neither charles  nor william and harry  receive taxpayers  money from the civil list. however  the prince of wales did receive over £4m from government departments and grants-in-aid in 2003-4. the duchy last year generated almost £12m. the prince has voluntarily paid income tax - currently 40% - since 1993.