Dutt was convicted under the Terrorist and Disruptive Activities Act (TADA) for possessing an AK 47 rifle after the 1993 Mumbai blasts. His appeal against his conviction is pending in the Supreme Court.
Digvijay Singh told reporters: "My personal view is that Sanjay should not have been tried under the TADA. He is not a terrorist."
He said Sanjay's decision to join politics and the Samajwadi Party was his own and the Congress would not react to it.
"However, as far as Priya Dutt's statement that she should have got a Congress ticket for him is concerned, I would say that it should have been at Sanjay's initiation and interest if he wanted to join us," he said.
Priya, sister of the actor, is a Congress MP from Mumbai and had expressed her disappointment over the actor joining the Samajwadi Party since their family is loyal to the Congress. She had added, however, that it was the actor's personal decision and there was no family feud over it.
When asked about this, Singh said: "It is their personal matter. But for us, the Dutt family is very respectable and Sunil Dutt (Sanjay's father) was not only a Congress leader but also a very respected social worker".
The Samajwadi Party had announced Sanjay's candidature from Uttar Pradesh capital Lucknow and stated that if Sanjay was not allowed to contest from there due to legal reasons, they would field his wife Manyata