Car manufacturers did not give retailers sufficient warning of supply shortages resulting from the September 1 introduction of the Worldwide harmonised Light vehicle Test Procedure (WLTP) and real driving emissions (RDE) legislation, AM’s latest survey results show.

In response to AM’s June/July survey seeking insight into impact of the new fuel economy and emissions test regimes, 55.6% of respondents said their manufacturer partner had communicated the possibility of stock shortages in the plate-change month.

Four months later, it appears that vehicle supply shortages – a result of manufacturers’ efforts to re-homologate their ranges under the new rules – were greater than many retailers were informed.

Just more than 90% of respondents to a follow-up survey – conducted between October 1 and November 12 – said their dealership suffered a shortfall in supply during September.

Of those, 67.6% said the impact on vehicle supply had been ‘severe’, 22.3% described it as ‘moderate’ and 10.1% found the effects were ‘mild’.

New vehicle registrations data for September illustrated that supply issues have varied from franchise to franchise.

While Mitsubishi (up 35.4%) and Volvo (up 7.6%) – which confirmed its range’s WLTP compliance in May – were among brands that appeared to have prepared well, Volkswagen Group brands accounted for almost half (49%) of the UK’s total September registrations decline of 20.5% (87,336 vehicles).

Less than a third of respondents (30.5%) to AM’s October survey said manufacturers had effectively communicated the legislation changes to consumers – up 10.2ppts on June/July.

This is reflected in the impact seen on retail sales.

In June/July, 29.1% said retail sales had decreased as a result of WLTP/RDE, with 61.9% seeing no impact.

Four months on, 67.3% said retail sales had declined, with 20.3% seeing no effect. The remainder, 12.4%, said the changes had resulted in increased retail sales.

A similar effect was felt on fleet registrations, where 31.4% of respondents had said in June/July that sales had decreased as a result of WLTP/RDE, compared with 59% who had seen no effect.

October brought a shift to 54.3% claiming a fall in fleet sales, with 7.2% claiming to have seen an increase. 38.6% said they saw no effect on fleet sales.