The waiting period can be a problem if delivery of a car is postponed until the unit is fitted.
Members of the Association of Car Fleet Operators London West region heard that the problem first appeared when the use of hand-held mobile phones while driving was banned last year.
But, months after the law was introduced, there are still some supply problems, the meeting was told.
One fleet manager said at the meeting: ‘A four-week wait is ridiculous. I would have thought it would be three to 14 days maximum.’
Other members said that a lead time of four or five days would be acceptable.
To tackle any problems, another fleet manager said she used her leasing supplier, simply stating that vehicles should be delivered with a compatible hands-free kit. She added that the cost was no different to other fitting services and there were never any delays.
However, members said that with the growing availability of Bluetooth technology, fewer vehicles needed to have hands-free kits fitted at all. With Bluetooth, the mobile phone communicates wirelessly with the car’s speaker system, allowing hands-free discussions.
Despite this, safety organisations warn that drivers should never use any phone while driving, even if it is hands-free, as any call is a distraction from driving that could lead to an accident.