Pakistan's top court has summoned the government's anti-corruption chief over a letter he wrote criticizing the tribunal's judges.

Chief Justice Iftikhar Chaudhry on Thursday issued a court order for the anti-corruption chief, Fasih Bokhari, to appear before the tribunal on February 4.

Bokhari has been ordered to explain a letter he wrote earlier this week to President Asif Ali Zardari, accusing Supreme Court judges of trying to influence upcoming parliamentary elections.

Chaudhry says the letter amounted to interference in court matters and was an effort to incite against the judiciary.

The development is an indication Bokhari could be charged with contempt of court.

Bokhari's clash with the judiciary stems from his refusal in mid-January to arrest the prime minister over a corruption case involving kickbacks allegedly taken by the premier.