"I have always argued that it is a scandal that Gilad Shalit was not released ages ago. It does not serve the Palestinian cause to keep him imprisoned," Mankell told the Christian daily Dagen.
Mankell was responding to criticism from Swedish MEP and former Christian Democrat party leader Alf Svensson, who has accused Mankell of only standing up for international law with regards to the plight of those living in Gaza under Israeli blockade.
"All I do concerns a struggle against oppression and discrimination. Why would I be against it in one area and not in another," Mankell told the website, arguing that the imprisonment of Shalit is in breach of the "most elementary humanitarian principles".
Henning Mankell, creator of the Wallander series of books, is the most high profile of the eleven Swedes who participated in the Freedom Flotilla to Gaza in May that was attacked by Israeli troops resulting in the deaths of nine Turkish activists.
Gilat Shalit was kidnapped in June 2006 by Palestinian forces, the first Israeli soldier to be captured since 1994. His case has generated a great deal of media and public interest in the aftermath of the flotilla attacks and his continued captivity was cited as a reason for the Israeli war in Gaza in November 2009.
Hamas has demanded the release of a thousand Palestinian prisoners in return for handing over Shalit. Israeli prime minister Benjamin Netanyahu agreed to the demand last Thursday but at the same time ruled out allowing Hamas to decide over the prisoners to be released.