Amber Harrison hired big gun Julian Burnside QC as battle with Seven escalates

Amber Harrison has hired prominent barrister Julian Burnside QC as her high profile  battle with Seven West Media moves to a new level.

Mr Burnside has confirmed that Ms Harrison will now counter sue her former employer after Seven escalated legal action over the release of confidential documents relaying to her ill- fated affair with Seven West chief executive Tim Worner.

Mr Burnside told the NSW Supreme Court that the matter needed to be switched to the Federal Court because Ms Harrison's cross claim relates to "substantial issues" under the Fair Work Act.

Justice John Sackur said he was inclined to agree with the switch to the Federal Court because the NSW Supreme Court does not have jurisdiction for Fair Work matters.

"It seems sensible that this should go to the Federal Court," Justice Sackur said.

Counsel for Seven David Thomas said the proposed move to have the case heard in the Federal Court came as a surprise.

However, Mr Thomas told Justice Sackur that his client wanted the Fair Work matter struck out of the cross claim.

Justice Sackur is yet to decide whether to release Ms Harrison's cross claim to journalists covering the case.

"I would normally accommodate the media under relevant legislation," Justice Sackar said.

However, he has asked representatives for Ms Harrison and Seven to reach an agreement on whether the documents should be released.

Amber Harrison - a former executive association at Seven - is under a temporary gag order preventing her from releasing more confidential documents allegedly gathered before leaving the media company.

Ms Harrison left Seven in 2014 after signing a confidentiality agreement that prevented her from speaking publically about Seven or her affair with Mr Worner.

The case is scheduled for a hearing in July but this could change if the matter switches to the Federal Court.

A hearing on Seven's request to strike out Ms Harrison's claim under the Fair Work Act has been set down for April 6.