By Reuters Staff (Adds background, details) May 26 (Reuters) - National Australia Bank Ltd on Wednesday said issues related to underpayment of staff for part-time work had impacted 3,200 current and former employees. The country’s third-largest bank also noted a local media report that said the Finance Sector Union was looking to lodge Federal Court proceedings against the bank for alleged underpayment of staff. The bank denied allegations that the underpayment issues impacted full-time employees, adding that it had already paid all current employees affected by the problem and was contacting former employees for payment. NAB said employees who worked in full-time capacities were unaffected by payment complications as “hours of work are not used to formulate their salary”.