FORMER Labor MP Craig Thomson plans to claim his mobile phone was hacked when he defends himself against allegations he called an escort service in 2005 and 2007.

Mr Thomson will deliver his critical speech for the defence to Parliament on Monday.

News.com.au has learned a top Sydney criminal barrister advised the controversial independent MP on how someone could call a third party and make it appear the call came from his mobile.

Mr Thomson is expected to use the advice in his address, which is expected to last for 15 to 30 minutes and could decide his fate as MP for Dobell.

The Fair Work Australia report on Mr Thomson's spending while national secretary of the Health Services Union produced explosive detail of telephone calls apparently originating from his mobile phone.

Telephone number impersonation - known as "spoofing" - is not new but has escaped the attention of other examples of phone hacking.

For a price, someone's number can be sent to a specific web site and the user can simply type in the number they want to impersonate, the destination number, and send a message.

Other forms of spoofing include email spoofing, IP spoofing and SMS spoofing.

Mr Thomson has been accused of calling an escort service three times in April, 2005, and again in August 2007, with services paid for on his HSU credit card.

Mr Thomson has denied the allegations and blamed unnamed enemies within the union who wanted to damage his reputation and his career in politics by linking him to prostitutes.

He said in a Nine Network interview, "I was in a very dysfunctional union for a long time and in about 2004, amongst a whole range of other threats that were made to me, one was that they would ruin my potential political career ... by setting me up with hookers.''

Prime Minister Julia Gillard this weekend leaves for a NATO summit in Chicago and will not be here for the speech.

But Opposition Leader Tony Abbott and senior Coalition figures will be paying close attention.

Yesterday the Australian Electoral Commission cleared Mr Thomson of charges he illegally used HSU funds for his successful bid to win the central NSW seat of Dobell in the 2007 election.

The AEC found the money had been declared or did not need to be declared because it was spent before the campaign period or was below a spending threshold.

And civil action based on the FWA report might not proceed because the alleged incidents happened too long ago.

Mr Thomson indicated on Twitter that he would use mistakes in the Fair Work Australia report highlighted by the AEC to discredit some of its other findings.

Liberal Senate Leader Eric Abetz said a phone hacking defence wouldn't explain how phone calls were made from Mr Thomson's hotel room and appeared on his hotel bills.

"I look forward to Mr Thomson’s detailed explanation to the Parliament next week, but I think it's fair to say that so far at face value these sorts of excuses or theories just simply don’t hold water."