A culture of wasteful spending by the General Services Administration, the real estate agency for federal buildings, comes under scrutiny at four congressional hearings this week.

Two House and two Senate committees are expected to range well beyond revelations that the federal agency spent more than $800,000 for a conference in 2010 at a Las Vegas resort.

One GSA executive who is a focus of the investigation is refusing to testify voluntarily and has been subpoenaed to appear.

His lawyer says the witness will assert his constitutional privilege to remain silent.

The House Committee on Oversight and Government Reform conducts the initial hearing Monday.