I refer the right hon. Member to the answer I gave to her on 10 March 2009, Official Report, columns 262-63W.
In addition, table 14 in “The Effects of Taxes and Benefits on Household Incomes, 2006-07”, http://www.statistics.gov.uk/elmr/07_08/downloads/ELMR_Jul08_Jones.pdf, presents information on spending on VAT, on average, accounted for by households in each income decile.
The Treasury has made no such assessment, but from these proportions it is possible to infer the estimated annual cost of the VAT rate reduction by income decile (although such estimates would be unreliable).
No such estimate has been made.