It is alleged the shares, in unlisted US telco Iridium Holdings, were about to explode in value when they were transferred to BVI-registered Trexton International Limited in September 2009.

The liquidator of Dr Walker's investment company, Apsara Capital, on Friday launched legal action against Dr Walker and Singapore-based businessman Georges Daniel Mercadal over the transaction.

Since founding healthcare group Aspen Medical in 2003, Dr Walker and school friend Glenn Keys have built the company into a profitable enterprise that employs 2200 people and boasts former health minister Michael Wooldridge on its board.

The Victorian Supreme Court lawsuit is the latest bout in a long-running stoush between Dr Walker and Sonic Healthcare founder Michael Boyd, whose listed group Fulcrum Equity sold the Iridium shares to Apsara in 2009.

Fulcrum was to receive $5.2 million, plus a share of the upside if Iridium, which runs a satellite phone network, went well upon listing on the NASDAQ exchange.

However, Fulcrum allegedly received only a $1.4 million downpayment, contributing to financial stress that resulted in the company being delisted from the ASX in August 2010.

In a statement of claim lodged with the court, Apsara liquidator Ross Blakeley, of FTI Consulting, alleges that by May 2009 Dr Walker and Mr Mercadel had ''a plan or common intention'' to divert the shares from Apsara to Mr Mercadel's Hong Kong-registered company, Corsair Capital.

Early the following month, the Iridium shares were transferred from Fulcrum to Apsara.

It is alleged that at some time in September 2009, the shares were moved from a US vehicle to Trexton, which at the time was owned by Apsara and run by Dr Walker as sole director.

But on September 27, Mr Mercadal was allegedly appointed as a director of Trexton at the same time as Dr Walker resigned from the board and Apsara transferred its ownership of Trexton to Corsair.

The bundle of shares carried two entitlements in the event that Iridium listed on the NASDAQ: US$3.1 million in cash plus 1.2 million shares in the listed entity, Iridium Communications.

It is alleged that when Iridium successfully listed a few days later, Apsara received the cash component and used it to pay off most of a loan from Stewartville, a company run by Melbourne businessman Geoffrey Tauber, that was used to finance the deal.

However, the Iridium Communications shares, worth about US$10.8 million, were allegedly issued to Trexton.

The following October, the shares were allegedly transferred to two companies associated with Mr Mercadal, Whitehill and Imperator Investments.

The liquidator alleges most of the shares were sold but some ''continue to be held by entities controlled by or associated with Mercadal''.

However, in March 2010 Corsair did pay Apsara about $876,000, which was used to pay off the remaining amount owed to Stewartville.

Mr Blakeley claims the transfer from Apsara to Trexton was ''at gross undervalue'' and ''without any benefit to Apsara''.

He alleges Dr Walker ''improperly used his position to gain an advantage for himself or someone else, or cause detriment to Apsara''.

Mr Mercadal either ''wilfully shut his eyes to the obvious'' or, together with Dr Walker, was part of ''a dishonest and fraudulent design'' to divert the shares, he said.

The liquidator asked the court to order Dr Walker and Mr Mercadal to pay damages and return the proceeds of the alleged diversion.

Mr Mercadal could not be located and Dr Walker could not be reached through Aspen Medical's spokesman on Wednesday morning.

Neither has yet filed a defence. A directions hearing has been set for May 2.