By BBC Correspondent Daniel Lak in Delhi

It has been a bruising day for the government.

Parliament has been debating the nuclear tests which surprised people in India and around the world and led to international criticism and economic sanctions.

The prime minister, Atal Behari Vajpayee, began the debate by pleading for consensus to continue, and reiterating India's view that its nuclear programme was peaceful.

He told MPs that India would only use its nuclear weapons - if ever - in self defence, and he reiterated a four year-old offer to discuss a "no first use" agreement with neighbouring Pakistan and others.

Risking an arms race

But the opposition was having none of it.

Almost every opposition speaker in the debate so far condemned the government's motives and what some said was a grave risk of an arms race in the region.

The largest party opposing the government, the Congress, which was in power when India's first nuclear test was conducted in 1974, demanded evidence of deteriorating national security that the prime minister said was behind the decision to test.

A veteran communist leader said ministers were being too provocative in the wake of the tests, and risking a regional arms race.

The thrust of most opposition criticism is that the government took the decision to test because of domestic political compulsions rather than national security - an accusation that has already been angrily denied by the government.

Some speakers taunted ministers by saying internal problems in the governing coalition seem to have disappeared now that the nuclear tests have gripped the nation.

Tests still popular

But the replies by ministers have mostly been measured and Mr Vajpayee can be expected to be more emphatic when he rounds-off the debate on Thursday.

In the end it is hard to see that any real damage is being done to the government. The indications are that most Indians are behind these tests, but also want the government to act quickly to deal with economic decline, unemployment, and other problems.