Nearly 300,000 "attempts to access websites categorised as pornography" were made from computers within the British Parliament in the last year, official records show.
The figure - which represents more than 800 per day - was released by Palace of Westminster IT chiefs in response to a freedom of information request.
It covers devices linked to the Parliamentary Network, including those used by MPs and peers, their staff and other employees.
Officials sought to play down the significance of the total, insisting it was inflated by pop-ups, auto-refresh and other web design features and did not reflect deliberate efforts to access sexual content.
They are also investigating the reason for wide variations between the monthly figures - with as many as 114,844 in November but just 15 in February.
"We do not consider the data to provide an accurate representation of the number of purposeful requests made by network users due to the variety of ways in which websites can be designed to act, react and interact and due to the potential operation of third party software," a House of Commons spokeswoman said.
Visits to otherwise blocked adult sites "may nevertheless be recorded in this dataset depending on website design", she added.
The figures were obtained by the Huffington Post UK website.