London ambulances are less efficient than many others in Britain, because for more than five years their crews have refused to operate a simple push-button communications system unless they are paid to do so.

John Moss, assistant chief of the London ambulance service, said recently "It is very sad and frustrating that the new communications system - new five years ago, that is - became tied to pay negotiations in 1972, and then with the subsequent productivity deal sought by the men."

The productivity pay negotations still are dragging on, and will come up again at talks with employers later this month. Meanwhile, the 300 units, installed - then removed - in 1972 as part of a plan to improve the London services communications network, are aging.

"Time catches up with machines as well as with humans. Ironically, I know of at least eight other area ambulance services in Britain that now have far more sophisticated and effective communications that our mothballed units could provide," Moss said.

The units were removed from London's 300 first-echelon ambulances only six weeks after their installation, when the pay impasse began. They are small boxes with five push buttons which would give Waterloo Control, handling between one and four calls a minute, a far clearer picture of ambulance availability.

The various buttons would inform the control center instantly whether an ambulance was answering a call, arriving at a hospital, had delivered patients and was again available, was at the scene of an emergency or back at base. At present the center is informed only when crews have delivered their patients.