"I am greatly saddened by it," Singh told media persons on the Gujarat government's decision to ban his book Jinnah -- India, Partition, Independence.
"The day we start banning books, we are banning thinking," said Singh, who was expelled by BJP for the book in which he has praised the Pakistan founder M A Jinnah.
He said the step taken by Gujarat government was "another example of (action taken against) Salman Rushdie and Satanic Verses," which was banned for its controversial contents on Islam.
Asked to comment on BJP's contention that he had been expelled for his uncharitable comments in the book against Sardar Patel and that his views on Jinnah were different from those of L K Advani, he said, "Let me understand why (I was expelled). Nobody has told me."
On his continuance as MP from Darjeeling, he said he got a telephonic call from his constituency that the people there wanted him to continue as their representative in Lok Sabha.
The Gujarat government on Wednesday night banned Jaswant's book on Jinnah alleging it was an attempt to defame the image of the country's first Home Minister Vallabhbhai Patel by 'questioning his patriotic spirit'.
"Jaswant Singh's book questions the role of Sardar Patel during the partition of India as well as his patriotic spirit. This is an attempt to tarnish the image of Patel who is considered the architect of modern united India," a statement issued by the state government said.
"It is a bid to defame Patel by distorting historical facts," it charged.
"So, the state government has decided to ban the book with immediate effect for wider public interest," it said, adding, "As per the ban, there cannot be sale, distribution or publication of the book in the state."