The first scheme launched by a London borough to help residents switch to less polluting vehicles will close next month.
Merton Council said it would not accept new applications for the £1,000 grant after 1 September because demand had begun to taper off.
The grant was introduced last September, shortly after the expansion of the Ultra Low Emission Zone. It is available on top of the Transport for London scrappage scheme.
Despite allocating £1m to the scheme, just £363,000 has been spent so far.
Merton said it had approved grants totalling £448,000, but the process was not complete in all cases.
Cabinet member for transport, Stephen Alambritis, said: ‘We launched Merton’s own vehicle scrappage scheme to help people struggling with the cost-of-living crisis, and to help clean up the air we breathe.
‘The latest air quality data shows we’re succeeding in achieving that.’
A 2023 air quality report showed there were three locations in the borough where nitrogen dioxide had failed to decrease since 2022.
