Immigration Minister Peter Dutton has confirmed a police operation at the Manus Island detention centre on Papua New Guinea. PNG authorities - reportedly "guided" by an Australian Federal Police officer - at the Delta compound have been searching rooms and shouting at the men to leave.

Mr Dutton called on "well-intentioned" activists to stop encouraging the asylum seekers and refugees to remain in the detention centre.

The Australian Taxation Office has only one company in its highest risk category for tax avoidance and it's not a high profile technology business.

Four years ago, 13 of the country's biggest companies were in Q1, the ATO's highest-risk category for tax avoidance, but now only News Corp Australia remains, reflecting what is described as a secretive, aggressive approach to the ATO.

As the only company with a high-risk rating, News Corp faces continual audits and reviews.

News Corp declined to respond to questions by The Australian Financial Review about its tax-risk status.

On April 22, ATO officials at the Senate committee inquiry declined to answer questions by former Greens leader Christine Milne about the tax status of News Australia Holdings which holds most of News Corp's Australian subsidiaries. However, the Financial Review has confirmed with several sources that News Corp is the mystery company still in Q1.

Rupert Murdoch's media empire in the USA has siphoned off $4.5 billion of cash and shares from his Australian media businesses in the past two years, virtually tax free. Over the past 10 years, Mr Murdoch's companies here have paid income tax equivalent to a rate of 4.8 per cent on $6.8 billion in operating cash flows, or just 10 per cent of operating profits. Normally a company will return cash to its offshore parent by way of dividends from shares or interest from loans. These however attract withholding tax. News has justified its practice of "repatriating" cash - $1.3 billion only last year - by making a "return of capital" to its New York parent.

"As a result of doing nothing more than putting a new $2 company at the top of the Australian group they later returned that capital in cash and shares with little tax consequence." Had these recent distributions been classed as dividends, News could have contributed a further $1 billion in tax to the Australian public purse. Dividends incur withholding tax at a rate of 30 per cent.