Its share price fell 8p yesterday to 249p, taking the total fall in the past two days to 17 per cent. The stock is now 60 per cent below its peak and at its lowest level since early 1991.
The market has been nervous about Blenheim for some time. The company committed a serious blunder last summer when a cash-raising exercise was abruptly followed by a profits warning.
The City felt misled and it has neither forgiven the company nor forgotten about the episode.
A series of less significant problems has also dogged Blenheim. It grew quickly by acquisition and has found it difficult to shake off worries about accounting policies.
Blenheim's income stream can be irregular. The company earns most of its money from holding trade fairs, events which may be annual, biennial or even triennial.
The year before last it changed its year-end, making profit comparisons more difficult.
Investors have also had to digest several changes in senior personnel. Most notably, the managing director Philip Soar was replaced by Staffan Svenby last November. There are worries over Blenheim's exposure to Continental Europe.
This week's bout of the jitters was set off by a critical weekend press report detailing some of the company's difficulties. Blenheim responded yesterday, stating: 'The article gives a totally biased and misleading impression of the company's trading prospects as a whole.'
At 249p, Blenheim shares trade on a price/earnings ratio of 10.5. That represents a 20 per cent discount to the sector average and a 75 per cent discount to most quoted media companies.
The above-average yield of 5.1 per cent also suggests that the stock market remains less than convinced about growth prospects.