LONDON (Reuters) -- ***The Financial Times newspaper*** reported on Saturday that an attempt by a London-based terror group to buy half a ton of toxic chemicals was foiled after the supplier became suspicious and alerted police.

It said the group had attempted to buy 500 kg (1,102lb) of the toxin saponin from Amersham Biosciences late last year but the sale was refused after staff became concerned about the size of the order.

A spokesman for London's Metropolitan Police told Reuters on Saturday that police were "not prepared to discuss the matter" at this time.

***The Financial Times*** quoted experts as saying the chemical could have been mixed with another toxin, such as ricin, and smeared in public places, causing widespread poisoning.

Saponin is sometimes used in laboratories to enhance the transmission of molecules through biological cell walls, while ricin is highly toxic, with less than one milligram sufficient to kill an adult.

Lennart Arlinger, business development director of Amersham, said it was possible the would-be purchasers were looking to use saponin "as an enhancer of the efficacy of a biological weapon".

He told the paper the order was so large that it "raised a red flag" and encouraged further inquiries.

The order was refused and the company informed police in Britain and Sweden, where Amersham handled the order, he added.