Rakesh Sood, who was Indian Ambassador to Nepal from 2008 to 2011, said both sides have allowed the relationship to come to a "very very dangerous point" and that India should have found time to engage with Kathmandu as it pressed for talks on the issue since November.
"I think we have displayed a lack of sensitivity, and now the Nepalese have dug themselves deeper into the hole from which they will find it difficult to come out," he told PTI.
By going for a constitutional amendment for the new map, he argued, Nepal is converting what was a difference in terms of territorial perceptions into a dispute and making its position non-negotiable over it.
"We have a territorial dispute with China; our militaries are right now talking about disengagement'. We have a territorial dispute with Pakistan; our militaries are eyeball-to eyeball and there is firing across the Line of Control," Sood said.
"Is that how we want to visualize our border with Nepal by making it a dispute when we have shared an open border with free movement of people since the British days and which has continued after 1947 as well," he asked.
Asked whether China was behind Nepal's bold move,Sood said he did not believe Kathmandu has taken up the issue at Beijing's behest though he agreed that Chinese influence in the Himalayan nation has grown in recent years.
India's relations with China came under severe strain following the 2015 economic blockade against Nepal. Since then, China has been pumping in huge amount of financial resources in Nepal, helping the landlocked country in laying new roads including connecting it to China for transportation of petroleum and other products.
China is also planning to lay an ambitious railway network connecting Kathmandu and Shigatse in Tibet where it would join an existing railway line to Lhasa. China has also offered Nepal four ports for shipment of goods to the landlock country which previously had to rely heavily on routes through India.
Prof S D Muni, a noted strategic affairs expert, said the bigger message from Nepal's action was that the Nepalese are asserting themselves and the old framework of special relations is gone completely.
"They do not care about it. You will have to deal with Nepal differently, with little more sensitivity and with little more tact and understanding. It is a new Nepal. Over 65 per cent of Nepalese are very young people. They do not care about the past. They have their aspirations. Unless India is relevant to their aspirations, they would not care," he said.
On whether India erred by not responding to calls for talks by Nepal, Muni too said: "There are lot of areas where India has shown complacency and over-confidence in dealing with smaller neighbours. Nepal is no exception to that."
Ambassador Ranjit Rae, who served as Indian envoy to Nepal between 2013 and early 2017, said Prime Minister K P Sharma Oli decided to go ahead with the new map just to consolidate his position in domestic politics. Rae said Oli would have gone ahead with the move even if there was a dialogue on the issue between the two sides.
"This sort of playing up anti-India sentiment had helped him in winning the elections and he thought it will again help him now as he is under lot of domestic pressure," he told PTI.
"I think it is related to Oli's insecurity domestically as his position in Nepal is quite weak. There have been a lot of demonstrations in Nepal for the government's failure in the economic front, on managing Covid-19. There have been rumours within Nepali Communist Party that there may be a change in leadership. I think this has been a lifeline for Oli," he said.
Rae said Nepal's decision to go for the constitutional amendment will make the issue more complicated to resolve.
"I think it is going to complicate the relation rather than improve them. It will make the issue more intractable. I agree that since November they have been saying that they wanted to talk but for one reason or the other talks were not immediately possible," he said.
"But we did say that we will talk after the coronavirus crisis is over. So there was no pressing urgency for Nepal to go ahead with the constitutional amendment. After all the issue has been pending since 1997; so another few months would not have made such a big difference," said Rae.
Muni, a professor emeritus in Jawaharlal Nehru University, also said India's Neighbourhood First policy derailed as its implementation was allowed to "go berserk".
Ambassador Sood expressed dismay over India not responding to Nepal's call for talks on the sticky issue, saying New Delhi should have found time to engage with the neighbouring nation.
"Everyday we keep reading that our prime minister has had virtual meetings with 50 of his counterparts, our external affairs minister has had virtual meetings with 70 of his counterparts; surely it should have been possible to have a meeting with the Nepalese officials at some level or the other - foreign minister, foreign secretary or at the level of the prime minister," he said.
Referring to the Neighbourhood First policy, Sood wondered why India should tell Nepal that it will talk on the matter only after the coronavirus crisis is over.
"We keep saying that we have a very close historical, cultural, linguistic and religious affinity with Nepal. Then why be so insensitive that we cannot find time to talk to them for more than 5-6 months. They raised the issue in the month of November and that time there was no Covid crisis," he said.