A full moon has been blamed for many things, including lunatic behaviour and growing a thick coating of bodily hair once a month, but now BT has linked it to increased use of mobile phones.

Cyclical troughs and peaks in the calling behaviour of 2000 volunteers in the UK were noticed to closely match the phases of the moon. More households were found to use the phone or dial into the internet during the seven days leading to a full moon.

Researchers for BTexact's Digital Living Programme made the connection while collating data to help BT develop applications and services that match customers' demands, and plan the network.

Stewart Davies, BTexact's managing director, said: "There is definitely a 29-day cycle in the number of households making calls. The call patterns are a series of peaks and troughs, and we identified a trough on the first day and a peak after 29 days.

"Just out of curiosity we matched the cycle against the phases of the moon, and discovered that the peaks coincided with days leading to a full moon."

Davies said the link could be "pure coincidence", but added: "It does look as though certain phases of the moon encourage more people to pick up the phone for a chat or use the internet, while other phases make us more taciturn."

The findings may even change the way BT works. Davies said if a link can be conclusively proved, it "could well make a difference to the way that we dimension our communications network and implement marketing campaigns for call stimulation".

Roy Gillett, president of the Astrological Association of Great Britain, said: "This is very exciting news because it supports what astrologers have been saying for many years - during the time leading to a full moon there is a build-up of creative and emotional energy. This may well manifest itself in humans as a need to communicate more frequently and for longer periods."

A BT spokesman would not comment on rumours that Mystic Meg will be used for a future advertising campaign.