A court in Pakistan has issued a ruling which could mean President Asif Ali Zardari having to quit as joint head of his Pakistan People's Party (PPP).

The Lahore High court said Mr Zardari could not take part in "political activities" while also head of state.

However, it set no date for him to cease political activities. He can appeal against the judgement.

There was no immediate response from the PPP or the president, who jointly leads the party with his son Bilawal.

Correspondents say Mr Zardari is unlikely to resign as PPP leader any time soon. He has the right of appeal which, correspondents say, could mean this ruling is challenged in the Supreme Court.

Mr Zardari's five-year term as president ends in 2013

The Lahore High Court issued the order in response to a petition brought by a group of lawyers, which challenged his position as both the president and the leader of the PPP.

In a 35-page ruling, the court said the president is not supposed to engage in political activities.

It said that the head of state needs to be neutral and non-partisan and therefore cannot hold an office in a political party.

"It is expected that the President of Pakistan would cease the use of premises of the Presidency for purposes and political meetings of his party," it added.