The drugs, known as "cognition enhancers" could improve brain performance in a number of ways, from sharpening short-term memory and increasing speed of thought.

The Academy of Medical Sciences has already advised ministers that the use of such drugs - commonly known as "cogs" - would be so widespread that they would need to be regulated.

Now Futurelab, an education think-tank, has taken the concept one stage further, warning that schools must be prepared to subsidise poorer children's use of such drugs to ensure they do not fall behind more affluent classmates.

In a Government-commissioned report, it said: "There are ethical issues about haves and have-nots. If cogs are only available to those who can afford to pay for them, what does this mean for equality in education?"

It follows warnings by doctors that otherwise healthy children - as well as their parents - are taking brain-altering medication such as Ritalin, prescribed for Attention Deficit Hyperactivity Disorder (ADHD), and Modafinil, prescribed for sleep disorders, to boost performance.

Around 40 "cog" drugs are known to already be in development by pharmaceutical and military firms.

The Futurelab report, based on research by Bristol University, warns that the side-effects of using them long-term is not yet known and their use throws up "a number of ethical issues".

But it adds: "If science can develop safe and effective drugs to boost cognitive performance why shouldn't society accept these as cognitive enhancements?"