A Health and Safety report into the London Ambulance Service has raised concerns about its radio comms network and vehicle panic buttons.
But a spokesman for LAS said all the problems had been fixed since the report came out.
The investigation in March found ambulance crews often working without radios - especially in heavy rain when Airwave seems to have reception problems.
Inspectors spoke to crews who also complained that ambulance panic buttons either did not work, or did not elicit any response when set off by staff, the Beeb reports.
But a spokesman for London Ambulance Service denied there were any problems. He said:
We have fully investigated the points raised about our Airwave radio systems in this report and followed the recommendations made.
The report of the panic button not working on a handset is an isolated incident, and an investigation has been carried out, including an independent investigation by a consultant.
Our staff are not expected to go out on ambulance calls without Airwave radios and our technical team carries out regular checks to ensure that all vehicles are equipped with the appropriate number of radios.
We have found no evidence of problems with Airwave radios during heavy rain. The safety of our staff is of the highest importance to us and we are committed to giving our technical teams all the support they need to ensure that staff and vehicles have robust systems in place to ensure they have fully functional radio communications.
Airwave, based on Tetra technology, is getting a £39m upgrade in time for the Olympics. The system doesn't work very well in buildings so extra kit is being installed in various venues where Airwave usage is likely to be high. ®