Illegal drug sites have fans in Parliament, as 484 page views had been logged for such sites via Parliament's network since January, a Freedom of Information request by the Huffington Post UK revealed.
A House of Commons official confirmed: "The information covers all sites accessed via all ‘non-public’ computers on the Parliamentary Estate and all users including Members of either House, their staff and staff working for the House Administrations."
In awkward timing, David Cameron was forced to apologise on Wednesday after jokingly accusing Labour MP Michael Meacher of taking "mind-altering substances".
The revelation about the websites that interest MPs, Lords and Parliamentary staff comes shortly after it emerged that over 300,000 attempts to access porn sites in a year had been logged via Parliament's network.
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But cyber-security expert Jay Abbott, from JustASC, told the Huffington Post UK that Parliamentarians could have good reasons to visit such websites.
He said: "The most important question to answer here is 'Why were these sites visited?' These visits may well have been sanctioned by superiors, or be part of a wider research programme on the mechanisms for illegal drug distribution in the UK.
"Only by having the equipment and expertise in place to look in granular detail at the circumstances behind this type of online activity inside the network can anyone actually determine the correct response."
Meanwhile, evidence of cocaine use was found inside the toilets at the Houses of Parliament in June. Traces of the class A drug were detected in nine toilets throughout the Palace of Westminster.
Parliamentary officials refused to disclose the names of the specific illegal drug sites that had been visited due to online security fears.
They explained: "This poses a high risk of enabling people to build up a picture of our security posture, products and policies (and therefore potential vulnerabilities). For instance, increasing the risk of ‘watering-hole’ attacks by providing data indicating what is, and is not, blocked by our systems from which, potentially, less well-protected websites visited by parliamentary users could be inferred."
John Simon, employment law partner at Shakespeares, said: “In most workplaces an internet policy would apply, which all employees would need to adhere to. Such policies usually state that visiting sites containing content of an unsuitable or illegal nature is not permitted and could lead to disciplinary proceedings."