Westpac Banking Corp., Australia's second-biggest lender, is posted to mark a steep fall, its biggest in 10 months in Sydney trading following the loan margins that were lower to the expectations of some analysts', with the company extending warnings on the outlook for profit growth.

The stock registered a 4.2 percent fall, triple the day's decrease on Australia's benchmark share index.

The squeeze was witnessed after Westpac announced to grab record profit for the six months ended March 31, with its cash earnings surpassing the average estimate among analysts surveyed by Bloomberg, as bad loans slipped.

"The focus has shifted very firmly from bad debts to underlying earnings power of the banks," quoted, Mark Harrison, who helps manage more than A$500 million ($456 million) at Sydney-based Macquarie Funds Group. "The net interest margin and the weakness here may be a cause for concern for the bulls."

The company's share marked a decline touching A$26.19 at the close, cut this year's gain to 3.5 percent.

Also, fiscal first-half profit clung to its record A$2.88 billion level, from A$2.18 billion the previous year, Sydney-based Westpac posted in a statement today.

Cash earnings of A$2.98 billion exceeded analysts' estimates of A$2.9 billion.