Mastercard is second only to Visa in the credit card market

Mastercard, which is owned by its 1,400 member banks, will sell 49% of its equity to investors. These shares will also carry 83% of voting rights.

The sale comes as credit card companies enjoy a boom in consumer borrowing and demand for the shares should be strong.

Mastercard is facing lawsuits after it lost an anti-competition case.

Closed shop

A Supreme Court ruled last year that Mastercard, along with Visa, had broken anti-trust regulations by not allowing member banks to offer credit cards with rivals.

After the verdict, American Express and Discover Financial sued Mastercard and Visa seeking damages.

We believe these resources will place us in position to defend our interests in the legal and regulatory arena Mastercard statement

Should Mastercard lose its legal battle, then it could face claims totalling many millions of dollars. Mastercard said it will retain $650m (�360m) from the IPO.

"We believe these resources will place us in position to defend our interests in the legal and regulatory arena," the company said in a statement.

After the sale, Mastercard's member banks will retain a 41% equity stake through non-voting class B shares.

A new Mastercard charitable foundation will hold 10% of the firm's equity and the remaining voting rights.