Teenagers who drink or smoke could be heading for "serious trouble" in adulthood, a heart expert warned.

A study of 1,266 English adolescents in England found those who consumed alcohol or cigarettes, even occasionally, were at increased risk of hardening of the arteries - before they left school.

Professor Metin Avkiran, associate medical Director at the British Heart Foundation which funded the research, said: "It is widely known smoking cigarettes and excessive drinking damage arteries which could lead to potentially deadly heart attacks or strokes.

"This study suggests the damage to arteries can occur even in the young, leading to serious trouble later on in life.

"Quitting smoking is the single best thing you can do to protect your heart.

"Our advice to everyone, including teenagers, is categorical - don't smoke and if you do try to give up as soon as possible.

"If you do drink, try to ensure that it's not to excess and within the recommended guidelines.

"The encouraging indication from the study is that the damage to arteries seems reversible, so it is never too late to make changes that may literally end up saving your life."

Known medically as atherosclerosis, hardening of the arteries can lead to a blood clot - increasing the risk of sudden death.

The study published in the European Heart Journal was based on data from Children of the 90s, the Avon Longitudinal Study of Parents and Children (ALSPAC) over a five-year period between 2004 and 2008.