‘if worse comes to the worse’ is not standard expression

The standard expression is, `if the worst comes to the worst’.

Examples: If the worst comes to the worst, you could always borrow money from me.* If the worst comes to the worst, the couple will have to postpone their wedding.* We could always sell our house and move to another city, if the worst comes to the worst.

Americans tend to say, `if worst comes to worst’. For example, if worst comes to worst, we’ll have to replace the captain. * If worst comes to worst, we’ll have to cancel our trip to Arunachal Pradesh.

Source: S. Upendran, The Hindu ‘Know Your English’ Series, March 6, 2006