Brokers have issued two downgrades this morning on prominent Australian companies. Firstly, Citi has downgraded Leighton Holdings (ASX: LEI) from Neutral to Sell following the allegations of impropriety, although risk management practices have improved. The broker applied a 10% discount to the valuation of the company. Qantas (ASX: QAN) has also been downgraded this morning by CIMB Securities from Outperform to Neutral. The broker believes that Virgin is gaining ground on the airline and earnings risk is increasing in the international division as competitors increase capacity. Despite this, the broker still prefers Qantas over Virgin on valuation.