Prime Minister Manmohan Singh is under severe pressure, his administration derailed from its legislative agenda by a series of corruption scandals that have come to dominate politics.

On Tuesday, police questioned a top businessman as part of a probe into one of the alleged scams.

Here are details on five major recent scandals:

TELECOMS LICENCE ROW

India may have lost up to $39 billion in revenue when the telecoms ministry gave out lucrative licences and radio spectrum in 2007/08 at below-market prices, the state auditor has said.

The Comptroller and Auditor General of India's (CAG) report in November also said rules were flouted when the licences were awarded, which led to many ineligible firms winning licences.

Telecoms minister Andimuthu Raja was sacked in November after the report was released. He was arrested this month on charges of misuse of ministerial office and criminal misconduct. Raja denies the charges.

The federal Central Bureau of Investigation (CBI) said this month it had arrested the managing director of India's DB Realty and vice chairman of Etisalat DB.

Etisalat DB is a joint venture between DB Group, the parent of DB Realty, and Abu Dhabi's Etisalat .

DB Group sold a 45 percent stake in Swan Telecom to Etisalat after the operator was granted a licence by Raja despite being ineligible. Since Swan Telecom has been renamed Etisalat DB.

The CAG report also said units of realtor Unitech were given licences despite not having adequate capital. The units are now part of the India operations of Norway's Telenor.

All firms have denied wrongdoing, and said they complied with all rules when licences were given.

The scam has had serious political implications Singh and his Congress party.

The opposition closed the winter session of parliament with its demands for a joint parliamentary probe, which the government rejected, saying separate investigations were underway.

ANOTHER TELECOMS SCANDAL

India's space agency is being probed by the CAG for granting a private firm lucrative mobile Internet bandwidth in 2005 without a proper bidding process that reports say has cost the government up to 2 trillion rupees ($44 billion).

Prime Minister Singh, who personally oversees India's space ministry, denied in early Feb. that any revenue had been lost.

Any political fallout may fail to gather momentum due to the case's complexity and the fact the satellites have not even been launched. But once again, Singh has been accused by the opposition of negligence.

The Indian Space Research Organisation (ISRO) leased transponders on two of its satellites to private firm Devas Multimedia, which granted it access to S-band telecom spectrum, worth billions of dollars to communication providers.

S-band spectrum, while not currently in extensive use, is likely to become increasingly valuable in India's rapidly-growing mobile phone market, with its ability to provide wireless broadband and other mobile data services.

The ISRO has moved to cancel the contract, admitting that it granted Devas improper access to a valuable national resource in a flawed contract that undervalued the spectrum.

Opposition politicians have demanded that Singh explain his role in the deal, as the former minister of state for space in 2005, while the law ministry said that they had recommended its cancellation last year, local media reported.

LOAN BRIBERY SCAM

Top officials of Indian banks, lenders and financial firms have been accused of taking bribes to grant corporate loans. While the size of the scandal is not known, local media have reported it could run into millions of dollars.

The CBI, India's federal investigative agency, arrested eight people in November, including the chief executive of LIC Housing Finance and senior officials at state-run Central Bank of India, Punjab National Bank and Bank of India.

The bribes were allegedly paid by private finance firm Money Matters Financial Services, which acted as a mediator and facilitator for the loan beneficiaries, the CBI said.

Three Money Matters executives, including the managing director, have been arrested for offering bribes.

Several leading Indian firms were named in court documents filed by the CBI, including wind turbine maker Suzlon Energy, infrastructure company HCC's Lavasa unit and real estate firm DB Realty.

l three have denied any wrongdoing. A CBI source has said the probe will widen to look if other banks were involved.

Finance Minister Pranab Mukherjee has asked investors not to panic over the case, following up on comments by other officials that this is a case of individual wrongdoing and not a widespread scam and that the banking sector will not be affected by it.

COMMONWEALTH GAMES

The sporting extravaganza in October, which cost up to $6 billion, was dogged by several cases of alleged corruption, including the purchase of equipment and issuing contracts. The anti-corruption watchdog has identified more than 16 projects with possible irregularities.

The Congress party has sacked Suresh Kalmadi from the post of chairman of the organising committee and as secretary of the party's parliamentary wing. Three of his close aides have been arrested and local media has said Kalmadi too could be arrested. His homes and offices were raided by the CBI in December.

The allegations include manipulations of tenders for building stadiums and other games infrastructure, and inflating bills for equipment including treadmills and toilet paper.

Several bodies, including the anti-corruption watchdog, the state auditor, the CBI and a special committee set up by Prime Minister Singh, are probing the allegations. The CBI has also raided the homes and offices of the Games organisers, part of a probe into $21.7 million of misplaced funds.

HOUSING SCAM

Congress party politicians, bureaucrats and military officials have been accused of taking over a plush Mumbai apartment block intended for war widows.

After the story broke in local media the government sacked the powerful chief minister of western Maharashtra state, who is a member of the Congress party.

Following a CBI probe, the environment ministry ordered the demolition of the 31-storey building in January, citing the violation of environmental and land-use rules.

The Arabian Sea-facing block with 103 apartments is built in an upscale Mumbai district that is among the world's most expensive pieces of real estate. Apartments were sold for as little as $130,000 each, while local media estimated their value at $1.8 million each.