Warning as you put up your tree on December 1st - fairy lights can slow down your broadband!

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

The watchdog estimated up to six million homes and offices could improve their broadband connection, saying wireless networks are often not set-up correctly or suffer “interference” from electronic goods including baby monitors and microwave ovens - and even festive fairy lights.

The free Wi-Fi Checker app, for smartphones and tablets, allows homeowners to test the quality of their internet signal and suggests ways to enhance it.

Ofcom also released research which found more than a quarter of homes in the UK have “superfast” broadband connection of more than 30MB per second - an increase to 7.5 million households from six million last year.

But higher-speed broadband is available in fewer than two in five (37%) homes in rural areas, the regulator found.

And around 8% of households, around 2.4 million, cannot receive a connection with speeds of more than 10MB per second, a figure which rises to nearly half of houses in rural areas.

This was often because caused by remote houses “lying further from the network’s local street cabinet or local telephone exchange”, Ofcom said.

Small businesses were struggling in particular with slower connections, as almost half are unable to achieve more than 10MB per second, and the watchdog estimated that by 2017 around 18% will still be unable to access superfast services.