Assertion: According to a few of the political parties in India, the emergency was necessary to control the deteriorating condition of the country's politics.
Reason: The Communist Party of India and BJP continued to back the Congress during the Emergency, believing that there was an international conspiracy against the unity of India.

The Assertion is correct but the Reason is incorrect.

Parties like the CPI (Not BJP) that continued to back the Congress during the Emergency, also believed that there was an international conspiracy against the unity of India. It believed that in such circumstances some restrictions on agitations were justified.