While the organisation's latest report show that verage values of used cars sold at auction across the board improved from £5,875 to £6,075, equivalent to a 3% increase, values for fleet product underperformed the market average, with zero growth recorded.

Looking at average prices, the fleet sector showed steady price growth in Quarter 1, but this seems to have stalled in April, suggesting demand is somewhat weaker now than it was earlier in the year and supply has increased following the March plate change.

The fleet sector along with dealer/px recorded the biggest percentage falls in conversion rates between March and April at 10% and 9% respectively.  Fleet sales have consistently recorded the lowest conversion percentages in 2011.

Andrew Hulme, NAMA chairman, commented: 'NAMA members have reported that trading conditions have remained challenging during the first half of May. Given the current level of demand, it is anticipated that the high level of stock will not be exhausted for another four to six weeks. Much of this stock has been multiple-entered in recent weeks and remain unsold simply because they are over-valued compared to market expectations – it is critical that these cars are cleansed from the system because average values are likely to fall further as we get into June and July.'