Weekly mortgage costs fell from £53.30 in 2007 to £48.70 in 2009 as the cost of all hosuing costs fell by £140.40 a year from £142 a week in 2007 to £139.30 a week in 2009.
But housing costs as a percentage of total expenditure has remained stable, decreasing by only 1% from 22% in 2007 to 21% in 2009.
Spending has remained relatively consistent for most other categories, with slight downward trends continuing for household maintenance and repair, and moving house costs.
With income groups split into 10 categories the highest income group spent £351.30 per week; more than twice the £139.30 average for all income groups and more than eight times that of the £40.40 average for lowest income group.
The highest income group spent £145.20 a week on their mortgage.
Researchers also found that UK households spent an average of £455 a week in 2009 compared with £471 in 2008, the first drop since 2001/02.
The biggest outlay was for transport at £58.40 a week.