BBC correspondent Daniel Lak reports on a 'tough session in parliament'

Opposition parties condemned the tests but Mr Vajpayee said India was now capable of producing nuclear weapons to deter aggression from Pakistan and China.

The series of five tests prompted widespread international criticism and led to economic sanctions by a number of countries.

But Mr Vajpayee insisted that India was only interested in self-defence and was committed to international disarmament.

"We do not intend to use these weapons for aggression, or for mounting threats against any country. These are weapons of self-defence to ensure that India is not subjected to nuclear threat or coercion," he said.

Critics not convinced

However, opposition politicians hotly criticised the government's stance, arguing that domestic politics was behind the nuclear tests, not national security.

Almost every opposition speaker in the debate condemned the government's motives. A senior Congress MP said there was no evidence of declining national security at the time of the tests and the motive was to build domestic political support. While a veteran communist leader said ministers were being too provocative in the wake of the tests, and risking a regional arms race.

Tests still popular

Despite the criticism Mr Vajpayee is expected to be more emphatic when he rounds-off the debate on Thursday.

The BBC correspondent in Delhi says that overall it is hard to see that any real damage is being done to the government with indications that most Indians are behind these tests.

The President of Pakistan, Rafiq Tarar, has said Islamabad is yet to make a decision on whether it will detonate a nuclear device in response to the Indian move.

Budget to beat sanctions

The new session of parliament will also see a new budget next Monday.

The need for tough measures to counter international sanctions and to curb unrelated economic slowdown might lead to higher taxes or less than expected social spending.

Although few real clues have emerged as to the government's intentions, reports say the finance minister may opt to speed up and deepen freemarket economic reform in part to compensate for sanctions.