For more than a decade, Ian Lazar has been a prominent fixture of Australia's shadowy second-tier financial market.

The lender of last resort has left behind a string of clients whose companies have been placed into receivership, whose assets have been sold off, and whose livelihoods have been ruined.

Mr Lazar offers to buy his clients' debt at a discount he negotiates with their bank, and says his pay-off is a cut of this discount.

But there are serious questions about precisely what the North Sydney mortgage trader does with his clients' affairs once they sign up.

Mr Lazar's modus operandi is consistent in each case examined by Four Corners: he targets people in financial difficulty who cannot refinance with a major lending institution.

He offers to help them out of trouble and talks up his access to a multi-billion-dollar fund that can buy out distressed mortgages.

Mr Lazar introduces his clients to solicitors, accountants and insolvency practitioners, but there are serious questions about the credibility of some of these advisers.

There are similar questions about exorbitant fees Mr Lazar charges and what work he actually performs to justify them.

Among his victims are graziers, small business owners, Aboriginal communities and even high-profile entertainment identities.

Lazar suspected of links to organised crime

Now, a Four Corners investigation has obtained affidavits tendered in civil proceedings which detail the suspicions of police that Mr Lazar may have been "involved in serious organised criminal activities".

And Mr Lazar is not alone. He operates in a world shirked by major lenders and largely ignored by the corporate regulator, the Australian Securities and Investments Commission (ASIC).

Mr Lazar's activities are not required to adhere to strict standards under a new national consumer credit regime, and ASIC says its priorities do not extend to policing business-to-business loans.

The result is a dimly lit marketplace with very little or no protection for large numbers of borrowers who are unable to obtain a loan from a major lender.

Mr Lazar claims he has enormous resources at his disposal to assist his clients.

"What I'm saying to you is this: today, I'm dealing with a fund in Hong Kong [of] $2.2 billion," he told Four Corners.

"Is it my money? No. Do I have access to it? Yes. I'm a mortgage trader. If the deal stacks up, there's no limitation for money now."

Mr Lazar has alleged he is being unfairly targeted by police and others. But several of his clients have told Four Corners he has repeatedly failed to deliver on his promises.

Second-tier lending market can be a 'frightening prospect'

Lawyer and UNSW business school lecturer Michael Peters says the second-tier lending market in which Mr Lazar operates can be a dangerous place for the unsuspecting.

He said financiers and mortgage brokers often "have the documents drafted prior to a default at the time the loan is made, to enable the creditor - the person obviously making the loan - to grab all the assets".

"There's caveats put on titles, their bank accounts are sequestered, cars are repossessed. So before the borrower has an opportunity to find out what's happened to their assets, they're basically gone.

"It's quite a frightening prospect for anyone."

ASIC told Four Corners that "borrowers need to be level-headed in these situations, as the lending contract is the means by which they may lose control of their business".

"They need to seriously examine their financial position and understand if they get involved in this activity they will not have access to consumer protections offered by traditional lenders to resolve disputes," it said in a statement.

Mr Lazar readily accepts that he has his detractors, but says he has "thick skin".

"There's a lot of people in the market - and it's no secret either - who try to character-assassinate me on a daily basis," he said.

Mr Lazar insists any suffering by his clients has been the result of poor decisions they made long before engaging his services.

Allegations of theft raised in Parliament by Senator John Williams

In 2011, Senator John Williams delivered a stinging attack on Mr Lazar in Federal Parliament.

"I rise today to talk on a most important issue that faces our nation, and that is the issue of people being ripped off by people laundering money, taking people's life savings and leaving them homeless and in dire straits," he said.

Senator Williams called for a royal commission into "white-collar crime" and cited several statutory declarations he tabled with his speech that had been signed by former clients of Mr Lazar.

One such client was entertainment impresario Kevin Jacobsen.

"Since the time that Kevin Jacobsen first met Lazar, which was less than one year ago, he has lost all his businesses and had all his trading companies placed in liquidation," Senator Williams said.

The senator also alleged that Mr Lazar stole Jacobsen's Lexus and falsely charged his American Express for $84,000 of bogus expenses.

Mr Lazar denied all of the claims in a detailed response, which was tabled in the Senate.

Tonight, Four Corners goes inside Mr Lazar's world and examines what he says is a unique business.

"I'm in a very complex business that people just don't get," he said. "Why others don't do it, I'm not sure."

The corporate watchdog has defended its actions in relation to Mr Lazar.

Four Corners aired claims that ASIC has declined to act on complaints that Mr Lazar has left clients with companies in receivership and ruined livelihoods.

ASIC says these cases were commercial transactions, not publicly available investments, and it does not generally intervene in such private disputes.

The regulator says it did take action back in 2004 to wind up another of Mr Lazar's companies, because that scheme targeted "mum and dad investors".

ASIC says it focuses on matters with a wider public impact, because it has limited resources.

Do you know more? Email besser.linton@abc.net.au.