Unsafe levels of a paint thinner chemical has been discovered in gravy granules just one week before families across Britain sit down to a Christmas roast dinner.

Lidl is recalling two batches of Kania Gravy Granules after they were found to be contaminated with xylene, which occurs naturally in petroleum and crude oil, the Food Standards Agency (FSA) said.

Exposure to the "harmful" chemical poses a health risk, causing irritation of the mouth, throat, nose and lungs and in severe cases leading to heart problems, liver and kidney damage and coma, according to Public Health England.

The products affected are 300g packets of Kania Gravy Granules for meat and for chicken with best before dates of October and November 2017. No other batches are thought to be affected.

The supermarket will display notices in all stores that sold the products, and customers are being urged to return the product for a full refund.