BEIRUT  - Lebanese Prime Minister Hassan Diab is suing the American University of Beirut (AUB), where he worked for 35 years as an academic, a spokesman for Diab said, in a dispute over his exit package from the financially struggling institution.

AUB, which has been hit hard by Lebanon's economic meltdown, declined to comment on the case.

Lebanon is grappling with a crisis caused by decades of state corruption and bad governance. A hard currency liquidity crunch has led to an 80% weakening of the local currency since October.

Diab presented his-long planned resignation in January - the month he became prime minister.

"... He asked for an exit package in line with common practices and precedents at AUB. This request was denied ...," the spokesman said.

Diab had "never made any special request for any payments to be made either in foreign currency or into foreign bank accounts. All AUB professors have their pensions paid in U.S. dollars, from a AUB foreign account", the spokesman said.

"What the PM expressed was only what was already stated in the AUB retirement plan regulations and policies."

The private AUB, founded in the 1860s, is alma mater of some of the Arab world's leading figures in politics, medicine, law, science and art. Its president told Reuters in May Lebanon's catastrophic collapse represented one of the biggest challenges in the history of a university which has weathered many crises, including Lebanon’s 1975-1990 civil war.

The state, which defaulted on its foreign currency debt in March, owes AUB’s medical centre - which attracts patients from across the Middle East and Central Asia - more than $150 million in arrears, AUB President Fadlo Khuri said.

(Writing by Tom Perry Editing by Peter Graff) ((thomas.perry@thomsonreuters.com; Reuters Messaging: thomas.perry.reuters.com@reuters.net))