if such lamps are used for illuminating your house

A number of retailers, particularly hardware stores, are selling rough service bulbs online.

But the National Measurement Office, the Government agency responsible for enforcing the ban on traditional bulbs, warned householders against buying the rough service versions.

An official guidance paper says such bulbs are "declared by the manufacturer as unsuitable" for illuminating household rooms and adds: "Consideration should be given to the terms and conditions of any household insurance policy if such lamps are used for illuminating your house."

A Defra spokesman said: "The final stage of the EU phase-out of incandescent light bulbs will mean that from September 1, 25W and 40W bulbs will no longer be allowed into the market. However, this does not prevent retailers selling existing bulbs they already have in stock."

DIY chain B&Q said it supports the shift away from traditional bulbs.