Bowen is using the nasty smell attached to tax havens to great effect

But it could also be a warning shot that a Labor government would be taking a closer look at the tax bona fides of offshore companies looking to purchase Australian assets.

Any move to restrict foreign investment must be done with particular care, in view of Australia's dependence on offshore capital and international trade.

The investment banking community doesn't seem too worried. They have had no indication from Labor that there will be further restrictions placed on offshore private equity investment - tax based or otherwise.

In this case the suitor, Canadian based investment firm Brookfield, already owns a string of large and important infrastructure assets in Australia thus has clearly jumped the FIRB hurdle on several occasions.

A letter sent this week from Bowen to the current treasurer John Frydenberg cites "transparency data showing neither party (Brookfield or its parent bidding entity) has paid income tax in reported years".

Brookfield's bidding vehicle is a Cayman Island registered company - which arguably seems like a red flag but it doesn't mean that the Australian operating company wouldn't pay tax.

Jurisdictions like the Cayman Islands are regularly used by funds as a place to aggregate investor capital before it is deployed into other countries. Profits on these investments will be paid by the investor.

But politicians understand the nasty smell that is attached to popular tax havens and Bowen seems to be using it to great effect.

The more important issue here is whether Brookfield's operating companies in Australia pay tax and how much.

Thus appropriate investigation of the history of tax payment by FIRB is both legitimate and important as it is for any company seeking to acquire Australian businesses.

Unfortunately Bowen's letter appears to place more importance on the particular assets Brookfield is buying rather than the principles around tax minimisation.

In particular the letter refers to the NSW government-owned Northern Beaches Hospital in Sydney which Healthscope has a 20-year licence to operate. It is one of a suite of hospital assets that are the subject of the Brookfield takeover.

Warringah independent contestant Zali Steggall has objected to the sale of this particular hospital, so it has become a hot issue.

Bowen sought more detail of Brookfield's FIRB approval process, whether there were any tax or competitions conditions attached whether or why there were any extensions given.

He has asked whether the treasurer inquired about the connections to low tax and secrecy jurisdictions such as the Cayman Islands or sought more information on the company's related-party framework - and more.

Bowen is applying acid to the government - suggesting in effect that the Coalition was inviting investment into Australia from companies that would siphon profits to the bank accounts of rapacious investors.

It is a sensitive issue given the much publicised legal tax minimisation antics of large US technology companies like Google and Facebook.

But the use of jurisdictions like the Cayman Islands is an entirely different matter.

Indeed the Australian Tax Office significantly tightened up the tax-free repatriation of profits on assets after TPG infamously pocketed $1.5 billion in profits on the sale of Myer.

It is the real gatekeeper in charge here because it advises FIRB on any tax-related risks. It assess the tax impact of earlier transactions undertaken by the applicant and its related parties plus any previous patterns of behaviour.

However, Bowen went to pains to point out that his queries around the Brookfield transaction were no reflection on FIRB.

And for its part Brookfield says, "the entity that operates the Healthscope assets is, and will remain, headquartered and registered in Australia and will therefore be subject to Australian tax law".

"The federal government has reviewed this transaction and has granted its approvals, including on tax grounds. We have always complied with all laws and regulatory conditions, including those relating to tax."