A move by Attorney-General George Brandis to restrict access to the government's chief legal adviser is unlawful and akin to keeping a "dog on a lead", a former top adviser to the Howard government has said.

Senator Brandis is at the centre of a political storm over a legally binding direction he issued before the July 2 election requiring all ministers, including the Prime Minister, to obtain his written approval before seeking advice from Solicitor-General Justin Gleeson, SC.

Mr Gleeson has flatly denied claims by Senator Brandis in Parliament that he was consulted about the change and said he would have protested it "in the strongest terms".

In a blistering submission to a Senate inquiry examining the controversy, former solicitor-general Gavan Griffith, QC, said the change brought to mind "the image of a dog on a lead".