SEOUL (Reuters) - South Korean President Park Geun-hye's office on Friday dismissed a claim by the leader of the opposition that she was planning to declare martial law as "irresponsible demagoguery".

Park's administration has been rocked by allegations that a friend used her ties to meddle in state affairs and wield improper influence, triggering calls for the president to be impeached or step down.

The opposition Democratic Party's leader, Choo Mi-ae, said at a party meeting on Friday that there was intelligence Park planned to declare martial law.

Park's spokesman, Jung Youn-kuk, said Choo's comments were "unbecoming of the leader of the main opposition party and are political demagoguery that is exceedingly irresponsible".

Park is under pressure from an angry public to step down with hundreds of thousands expected to gather in the capital on Saturday in the fourth straight weekend protest.

Park's father, Park Chung-hee, took power in a coup in 1961 declaring martial law and ruled until he was shot dead in 1979. He declared martial law twice more during his time in office.

(Reporting by Jack Kim and Ju-min Park; Editing by Nick Macfie)