India's President N. Sanjiva Reddy took the controversial step yesterday of dissolving Parliament and calling new elections for the fall that could catapult former Prime Minister Indira Gandhi back into power.

His actions were called unconstitutional by members of the Janata Party that defeated Gandhi in elections 2 1/2 years ago. They demanded Reddy's impeachment and insisted they have the votes to form a government under the leadership of Jagjivan Ram, who would have been the first prime minister from the untouchable caste.

Reddy, however, was "convinced" that "in the present unstable situation no party was in a position to form a stable and viable government," the president's politica secretary said.

Thus uncertainty continues to grip India, the world's largest democracy, as it faces its most serious political crisis since gaining independence from Great Britain 23 years ago.

Moreover, India's claim to be the most stable government on the South Asian continent appears shaken. With this present governmental crisis, it joins neighboring nations in some degree of political turmoil such as Afghanistan, Pakistan and Nepal.

Until the election is held in either November or December, India will be run by a caretaker government headed by Charan Singh, who was forced to resign Monday after 24 days as prime minister when Gandhi's followers withdrew their support of his administration.

He charged they refused to back him because he would not ease up on special court prosecutions of Gandhi and her son, Sanjay, on charges of misusing power and of corruption during her 1975-1977 emergency rule.

While her political fortunes appeared to be at rock bottom as recently as June -- when she faced those special court prosecutions and members of her party began deserting her -- Gandhi appears to be the major winner of the current political crisis.

She is the best known political figure in India, and her party is the best organized to wage a nationwide election campaign.

A public opinion poll recently showed that 68 percent of those questioned thought the country was better off under her government and almost half of them preferred her as prime minister.

Most Indian office holders oppose early elections because they fear they will be thrown from office on a tide of mounting voter indignation over chronic economic problems, labor unrest, inflation, deteriorating law and order, and increased warfare between religious and ethnic groups.

India's current crisis started July 28 when Morarji Desai, 83, was forced to resign as prime minister after mass defections from his Cabinet. Desai, who took over the government after Gandhi's defeat in 1977, was only the fourth prime minister in India's history.

The Cabinet defections were engineered by Singh, a 76-year-old North Indian whose power base is among the small farmers and landowners and who entered national politics just three years ago.

Singh beat out both Ram and Desai, who wanted another chance to form a new government, last month. But his victory was short-lived, and when he resigned Monday he recommended that Reddy call new elections. The next election is scheduled for 1982.

Ram, 71, asked Reddy for a chance to put together a parliamentery majority for a new government.

He said Redy had asked him to submit a list of his supporters to prove that he had the votes, but then the president called for elections without giving him his chance.

Ram denounced Reddy's action as "a severe blow to democracy" as his Janata Party supporters organized what they hope will be a massive protest rally for Thursday. They called on party workers throughout India to observe a protest day Friday.

Even Desai, who retired from active politics after losing the prime minister's job, said he might take part in the anti-Ready campaign.

He called Reddy's decision "absolutely unconstitutional" and said it is his duty to educate the people about the situation. "People are the only guarantee to keep democracy strong in India," Desai said.

Reddy, however, was dealing with an unprecedented situation without any guidance available from the Indian constituion. According to Reuter, legal and constitutional experts he consulted in India were divided on the question of whether he could call new elections or had to let the country stumble throught a succession of coalition governments.

One of the legal experts Reddy called, Nani Palkhivala, the former Indian ambassador to Washington, said new elections should be a last resort and denonuced Reddy's decision as "unjustified to the point of constitutional impropriety." the Associated Press reported.

However, India's famed bureaucracy moved into action within hours of the president's announcement. The chief elections commissioner ordered the electoral rolls updated and estimated 350 million Indians would vote.

Reddy said that Signh had assured him that his caretaker government would take no major administrative or executive actions.

The election should be the second on the subcontinent scheduled for this fall. Pakistan's military rulers have promised to hold elections in November that could return to power the party of Zulfigar All Bhutto, who was executied this spring by the present government.

Further to the west, the Soviet-backed government in Afghanistan is rocked by rebellions by Moslem tribesmen who claim to control the territory on three sides of the capital city of Kabul.

In Nepal, unrest has forced the king to call for a referendum that could change the form of government there.