Several opposition parties - including the Congress, the DMK, the AAP and some Left parties - returned to Parliament Wednesday afternoon after an unsuccessful protest march to the Enforcement Directorate's Delhi office Wednesday to file a complaint against the Adani Group over the Hindenburg report, alleging 'corporate fraud, political corruption, stock-price manipulation'.

What happened at the protest march?

Heavy security was deployed along the opposition leaders' march route; Delhi Police had set up barricades and used loudspeakers to urge the politicians to desist as orders banning large gatherings had been enforced.

After tense moments in the stand-off between the opposition politicians and Delhi Police, the former relented and trudged back to Parliament, where they vowed to go 'one by one' to meet ED officials and call for the inquiry.

"… we will go back to Parliament… will raise this issue again… and our delegation of 17-18 parties will meet ED," the Congress' Syed Naseer Hussain told reporters, adding, "We will go one by one… and lodge our complaints."

"If ED will not lodge the complaint they will be exposed. Then we will release that complaint to you and create a ruckus in the Parliament."

Earlier, Congress chief Mallikarjun Kharge slammed the centre for ‘not letting us anywhere near Vijay Chowk (where the ED’s Delhi office is)'

"All of us are going to meet the Director (of the) ED to submit a memorandum into Adani's scam… but they have stopped us. There is a scam of lakhs of rupees… LIC, SBI and other banks are destroyed," he told reporters.

Who was missing from the protest?

Bengal chief minister Mamata Banerjee's Trinamool Congress and Sharad Pawar's Nationalist Congress Party (which is allied with the Congress in Maharashtra) are not part of this protest march, news agency ANI said.

What does the opposition parties' letter say?

In a two-page letter the 16 parties urged the agency - 'which claims to pursue such cases with vigour and fairness… (but) has yet to launch even a preliminary inquiry' - to investigate 'a relationship that has serious implications not just for our economy but, most importantly, our democracy'.

In their letter to the ED - which cannot act unless there is a police complaint - the opposition cited accusations against the Adani Group that say it has established a network of offshore shell companies and offshore funds linked to the group 'for the purposes of (1) artificially inflating stock valuations and (2) to give a distorted picture with regard to the group companies' financial health'.

The opposition further claims a 'clear causal link' between the offshore entities and the Adani Group's Indian cos- a reference to Gautam Adani's brother Vinod, who they say is 'alleged to be the person crucial to setting up these networks'.

The letter also claims the group 'repeatedly exercised improper influence to obtain concessions and contracts from governments and regulated entities'.

The opposition claims a tender for re-development of Mumbai's Dharavi area, which it said was initially won by a Dubai-based company for ₹7,200 crore and then cancelled 'because of delays in the transfer of Railways land'. The revised tender, the opposition said, was won by the Adani Group - 'which has no known experience in urban redevelopment - for a sum over ₹2,000 crore lower.

Parliament stand-off over Adani JPC demand

The letter comes amid a fierce stand-off that has left Parliament deadlocked since it resumed sittings Monday for the Budget session, with squabbles between lawmakers from the ruling Bharatiya Janata Party and those from the opposition forcing adjournments at 2 pm on Monday and Tuesday.

Each time, shortly after resumption, both Houses were adjourned till 11 am the next day. This afternoon too, both were adjourned till 2 pm, with additional ruckus over Congress MP Rahul Gandhi's remarks at United Kingdom events.

The Adani-Hindenburg controversy

Since the Adani-Hindenburg furore broke in January, the opposition has held firm on its demand for a JPC, or joint parliamentary committee, to probe allegations against the Adani Group by United States-based short-seller.

The government has, so far, refused to accept this demand, although both finance minister Nirmala Sitharaman and Reserve Bank of India chief Shaktikanta Das have spoken on the strength of the nation's banking systems.

The Supreme Court has also become involved; this month it ordering the setting up of an expert committee of six headed by ex-Justice AM Sapre.

The top court's panel is to look into the massive slide in Adani Group stock prices that followed the publication of the Hindenburg report; the market valuation of the group dropped by over $120 billion in a matter of days.

The Adani Group has denied all charges by Hindenburg, has paid back some of it sizeable debts to allay concerns, and held roadshows to reassure investors.