The Commonwealth Bank of Australia (ASX:CBA), the country's biggest lender, stands to make an astonishing $1 billion in extra annual interest revenue by lifting its home loan margins over the last two years, according to data crunched by banking comparison website Mozo.com.au.

Over the last two years, including yesterday's 45 basis point gouge, CBA has increased its standard variable home loan rates by a total of 57 basis points over official cash rate movements.

According to the latest APRA monthly banking statistics, the Commonwealth Bank has a total of $248 billion in housing loans in Australia. Assuming 75 per cent of these loans are variable interest rates, the annualised effect of the bank's 57 basis point increase is $1B in extra revenues.

If ANZ, NAB and Westpac follow the Commonwealth Bank's lead and increase home loan rates by 20 basis points above the Reserve Bank, the Big 4 stand to earn a combined total of $3.7 billion in extra interest each year, Mozo said.

Rohan Gamble, managing director of Mozo said: "These figures show that it is absolutely time for increased regulation of the banking industry to finally put an end to the merciless gouging of Australian home loan customers.

"If the Big 4 banks are forced once and for all to end their cynical interest rate profiteering and keep rates in line with the Reserve Bank, either through increased regulation or competition, Australian mortgage borrowers will be billions of dollars better off each year."