The second half of the year looks set to see house prices drift back to where they were at the beginning of the year as buyers get the upper hand, according to the online estate agency portal.
Asking prices for properties posted on Rightmove have fallen 0.6% in the North West, from an average of £169,819 in June to £168,853 in July this year.
Prices in Yorkshire, East Anglia, London, and the South East have also dropped, whereas in the West Midlands and the South West Rightmove said there has been an increase in house prices in the past month.
Rightmove said the annual change has increased 2.9% in the North West from £164,132 in July last year.
Miles Shipside, commercial director of Rightmove, said: "More aggressive pricing is now the order of the day, which means that conditions are ripe for a strong buyers' market in the second half of 2010.
"The end of spring traditionally heralds a tougher time for sellers as the market goes into recess for the summer.
"The 123,507 new sellers that Rightmove has recorded coming to market in this month's index have reacted by asking an average of 0.6% less for their property than the month before. This is the first month-on-month fall in 2010, and with the likelihood of more economic pain to come, we forecast further downward pressure on new sellers' asking prices.
"Sellers are going to have to price at bargain levels and bullishly promote their properties in order to stand out from the crowd. Those sellers that act more quickly will be able to lock-in some of the price gains made in the last eighteen months. However, the tradition of testing the water at a higher figure before reducing at a later date will backfire in areas of excess supply, as over-ambitious sellers will have to cut back even more as they chase prices downwards."