The retailer yesterday (13 October) took its website off-line to "protect our customers and the public", as it began the process of removing pornographic titles from sale.
A report in the Mail on Sunday revealed that when searching for the term "daddy", a series of eBooks discussing topics such as incest and bondage were visible alongside children’s titles.
WHSmith apologised, claiming the majority of "unacceptable" eBooks to be found on its website were self-published through its partnership with eReader-maker Kobo.
It added it would not display any self-published material until it is "completely confident" that "inappropriate books" will never be shown again.
The high-street retailer said in a statement: "Last week we were made aware that a number of unacceptable titles were appearing on our website through the Kobo website that has an automated feed to ours.
"This is an industry wide issue impacting retailers that sell self published eBooks due to the explosion of self publishing, which in the main is good as it gives new authors the opportunity to get their content published.
"However we are disgusted by these particular titles, find this unacceptable and we in no way whatsoever condone them. It is our policy not to feature titles like those highlighted and we have processes in place to screen them out."
When our website goes back online it will not display any self published material until we are completely confident...— WHSmith.co.uk (@WHSmithcouk) October 13, 2013
that inappropriate books can never be shown again.— WHSmith.co.uk (@WHSmithcouk) October 13, 2013
We sincerely apologise for any offence caused.— WHSmith.co.uk (@WHSmithcouk) October 13, 2013