Karl Rove, the former White House advisor and the man considered the key figure behind George Bush's election successes, has defied a subpoena to testify before the US congress. 

Rove is accused of having used his position to influence partisan prosecution at the US department of justice and had been due to appear on Thursday before the House Judiciary subcommittee.

The White House has cited executive privilege as a reason the Rove and others who currently serve or have served in the administration should not testify.

It has argued that internal administration communications are confidential and that congress cannot compel officials to testify.

But that has been rejected by Democratic politicians on the panel that had summoned Rove, saying his claim of immunity is invalid.

Following his refusal to appear on Thursday they ruled that the former advisor was breaking the law by refusing to cooperate - a possible first step toward holding him in contempt of congress.

Rove was subpoenaed in May in an effort to force him to talk about whether he played a role in prosecutors' decisions to pursue cases against Democrats or in firing federal prosecutors considered disloyal to the Bush administration.

A decision on whether to pursue contempt charges now goes to the full Judiciary Committee and ultimately to Nancy Pelosi, the speaker of the US house of representatives.