The market capitalisation of THL has been fallen by more than a third, or $200 million, after the campervan sales and rental group warned it would miss profit forecasts.

THL, which has a fleet of 7200 rental campervans under brands including Britz, Maui and Apollo, and also a substantial business selling the vehicles, warned that profit for the year would be up to 31 per cent lower than a forecast issued in February.