INSTRUCTIONS on how to make the deadly poison ricin using everyday items are freely available on the internet.

Any terrorist with access to a computer can discover the formula and the production process in a matter of minutes.

They could make the killer agent on their kitchen table using castor plant beans, glass jars with airtight lids and coffee filters.

''It is certainly a very toxic, if not one of the most toxic substances which you can obtain with relatively straightforward means,'' said Peter Kaiser, of the Organisation for the Prohibition of Chemical Weapons.

The main ingredient is the castor plant bean. Ricin is a toxin derived from such beans, one million tons of which are processed around the world each year to make castor oil, which is used as a laxative and in automotive brake fluid. The chemicals themselves are

widely sold.

One website warns at the outset: ''This stuff is extraordinarily poisonous. Arsenic takes 100 granules to kill someone, ricin takes 1-2 granules.''

It adds: ''If you try to make this poison (kills in four days, no good cure and the cure is rare) you will probably get some on your skin and die. Now you see why kids back in the day (sic) didn't wanna drink that castor bean cough syrup.''

It suggests obtaining the vital component, castor beans, from a garden supply centre.

The process for making the toxin takes only a matter of days. The bean pulp and chemicals are reduced to a meal and can then easily be reduced further to a lethal white powder.

One thousandth of a gram of it is enough to kill. The only problem facing a potential terrorist is not to touch or inhale any of the deadly substance. Charles Shoebridge, a former anti-terrorism officer, said: ''You only need the knowledge or experience of a chemistry undergraduate to make it.''

However, Strathclyde Police last night dismissed any attempt to clamp down on the sale of castor beans.

A spokeswoman said: ''You can make a bomb in the kitchen with items such as sugar and weedkiller. However, you would not ban weedkiller.''

Ricin kills the body's cells by preventing them from making proteins. A small dose can be fatal if swallowed, injected or inhaled.

Ingesting ricin causes fever, stomach ache, diarrhoea, vomiting and eventually death. Inhaling ricin often results in death from respiratory failure in 36 to 72 hours. Injected ricin causes death from multiple organ failure.

Ricin is not easily absorbed through the skin and experts say it is not an efficient way of killing large numbers of people. It is estimated that four tons of ricin dispersed by aerosol would be needed to kill half of the people within an area of about 40 square miles, compared to only about 2lbs of anthrax.

Researchers at the University of Texas have been working on a vaccine and reported last year that it worked on mice. Doctors are at present only able to treat symptoms.

Ricin, developed during the second world war by the US and its allies, has a long

history of use in espionage, but experts say it is hard to use as an agent of mass death.

Its best known victim was Bulgarian dissident Georgi Markov, assassinated by a jab to the leg with a poison-tipped umbrella in London in 1978. He died a few days later.