ISLAMABAD: Switzerland has refused to reopen long-running graft cases against Pakistani President Asif Ali Zardari as he enjoys immunity as head of state, Pakistan's law ministry said on Sunday.

Pakistan wrote to Swiss authorities in October over the multi-million dollar allegations against Zardari, which date back to the 1990s, at the insistence of the country's Supreme Court.

Zardari and his late wife, former premier Benazir Bhutto, were accused of using Swiss banks to launder $12 million in alleged kickbacks.

Yasmin Abbasey, the top official in the law ministry, told AFP the Swiss had replied saying they would not reopen the cases which were frozen when Zardari became head of state in 2008.

"They have responded to the letter and said the president has immunity," she said.

"This was the main issue and they have confirmed it that the president enjoys immunity."

Pakistan's top court spent nearly three years demanding the government, led by Zardari's Pakistan People's Party (PPP) ask the Swiss to reopen the cases before they finally relented.

The tussle cost prime minister Yousuf Raza Gilani his job in June, when the Supreme Court convicted him of contempt for refusing to obey its orders to write to the Swiss, forcing him out of office.