BOSTON — Almost a third of all mortgage loans are approved because of false information and up to 20 percent of loans wouldn't be made if lenders knew all the facts, a mortgage expert says.

And consumers are picking up the tab.

Richard D. Ward, a former police officer who now works as president of Los Angeles-based Affinity Corp. said that the money lost to fraud shows up in higher prices.

"Consumers are paying for this, through higher loan costs, higher lending fees, and higher interest rates,'' Ward told the Mortgage Bankers Association convention Monday.

One of the most common forms of fraud is "property flipping,'' in which a property is bought and then resold -- or "flipped'' -- several times, each time at a falsely inflated higher price, among a single group of people.

The property is then sold to an unsuspecting mortgage company that, seeing the previous purchase and sale prices, pays much more for the property than its market value.

When the company tries to resell the property, it loses tens of thousands of dollars. Often, the property sellers can't be tracked down because they've left town or used fake names.

"In Boston and all over the nation, we're seeing a huge number of property flips,'' said Ward, whose firm helps clients avoid fraud by compiling nationwide statistics on individuals and companies in the real estate industry.

Jackson said the increase of online banking transactions in recent years made fraudulent activities easier, because of the ease with which computer users can create bank statements, verifications of employment, W-2 tax forms and other documents needed for mortgage applications.

David J. Kuff, an Affinity spokesman, also said the potential for fooling a bank or mortgage company increases as more people become involved in the transaction.

"There can be up to 44 different parties involved with a mortgage, from the termite inspector to the accountant to the real estate agent, and any one of them could be fraudulent,'' Kuff said.