Warning that Christmas fairy lights can slow your Wi-Fi

Watchdog finds festive angle as it launches app to test home broadband speed and releases findings that millions of British homes still lack high-speed access

Fairy lights on Christmas trees could cause slower Wi-Fi speeds, the UK regulator Ofcom has warned, as it launched a new app to test coverage in homes.

The watchdog estimated up to six million homes and offices could improve their broadband connection, saying wireless networks were often not set up correctly or suffered "interference" from electronics including baby monitors, microwave ovens and Christmas lights.