There is a difference between CPM's opposition and Bjp's opposition.
CPM's opposition is mainly because they are allergic to closer ties with the US, who they consider the most powerful imperistitic power in the world - the leader in the pack of all imperialistic powers.
The BJP's opposition is simply to prevent Congress taking the credit for a watershed deal and running away with BJP's urban vote base
In 1999, Vajpayee as PM and in 2000 Jaswant Singh as Foreign Minister of NDA, on the floor of the UN General Assembly categorically gave an assurance that India will refrain from nuclear tests, justifying such a position that India had no need to test.
This makes BJP's opposition to the deal most dubious
