A senior South Korean presidential official lashed out at North Korea Friday over its reported demand for huge economic aid in return for a summit with then South Korean President Lee Myung-bak.

Lee, who served as president from 2008 to 2013, said then North Korean leader Kim Jong-il, the late father of the current leader Kim Jong-un, first expressed his hope for a summit in August 2009, leading the two rival Koreas to begin behind-the-scene negotiations on the issue.

"North Korea demanded that Seoul offer the North 100,000 tons of corn, 400,000 tons of rice, 300,000 tons of fertilizer as well as asphalt pitch worth US$100 million and $10 billion to fund its establishment of the national development bank," Lee said in his memoir, "President's Time" to be released next week.

A senior secretary for President Park Geun-hye said North Korea's demand for money as a precondition for a summit is something that is "a surprise and unacceptable."

The official, speaking only on condition of anonymity because of the issue's sensitivity, made it clear that the government will handle diplomatic issues in a transparent manner.

His comment is the latest sign that Park does not have any intention to meet with North Korean leader Kim Jong-un if huge economic aid and other strings are attached to a summit.

It's not rare that North Korea has demanded huge aid in return for summit with South Korea.

Former President Kim Dae-jung was under fire from critics that he bought a summit with North Korean leader Kim Jong-il in 2000 after the revelation that Hyundai Group, one of South Korea's conglomerates, illegally transferred US$500 million to the North just months before the first-ever summit.

The senior secretary was also critical of Lee's memoir, which detailed secret inter-Korean negotiations meant to set up a summit, and Lee's summits with U.S. and Chinese leaders, saying South Korea's national interest won't be served by such a revelation.

Meanwhile, Kim Du-woo, Lee's former press secretary, defended the upcoming release of Lee's memoir, saying that Lee detailed his experience in foreign affairs and security in the book as the current government seems to be unaware of previous government's policies.

Lee penned the memoir to help a successive government in terms of policy continuity in state affairs, according to Kim.

Still, the trade of thinly veiled accusations by officials of the former and current governments over the memoir is widely seen as a clash between the former and the current governments. Former President Lee and President Park came from the same ruling party.

The latest public clash came as Park's job approval rating dropped to an all-time low this week.

The survey on 1,009 adults found only 29 percent of those polled approved of the way Park has been handling her job, down 1 percentage point from a previous week, according to Gallup Korea.

It marked the first time that Park's approval rating has tumbled to levels below 30 percent. (Yonhap)