Former real estate agent Gerard Baden-Clay remained composed under intense cross-examination at his trial, calling claims he killed his wife “absurd”.

Gerard Baden-Clay has emphatically denied suffocating his wife during an intense cross-examination at his murder trial.

The 43-year-old faced a barrage of questions from crown prosecutor Todd Fuller on his fourth day in the witness box at the Brisbane Supreme Court.

Baden-Clay said suggestions he killed his wife Allison and dumped her body underneath the Kholo Creek Bridge were absurd.

After several hours of cross examination on Wednesday, Mr Fuller accused Baden-Clay of smothering his wife as they struggled.

“You attacked her and the only way she could respond was to lash out and claw at your face and leave marks upon it,” Mr Fuller said.

“Probably as you smothered her and took her life from her.”

Baden-Clay said that was not true.

“I never did anything to physically harm my wife in any way, ever, so your suppositions to then take it further to suggest that I did other things as well, is absurd,” he said.

The former real estate agent also rejected accusations he “unceremoniously” dumped his wife’s body under the bridge, at Anstead in west Brisbane, where it was found on April 30, 2012.

“The suggestion that I would leave my children for any time, in the middle of the night, is absurd, let alone do the dastardly things you’re suggesting,” he replied.

Mrs Baden-Clay’s body was discovered 10 days after her husband reported her missing from their home in nearby Brookfield.

Mr Fuller accused Baden-Clay of covering his tracks and keeping up the facade of a concerned husband.

“I was a concerned husband and I am a very concerned father, I remain so. It’s not a facade,” Baden-Clay said.

He remained composed during the several hours Mr Fuller questioned him, in contrast to earlier evidence before his own barrister when he was reduced to tears several times.

Baden-Clay rejected suggestions he was under significant financial and personal pressure on the last day his wife was seen alive.

The court has previously heard he had large debts and had rekindled a long-running affair with former employee Toni McHugh.

On Wednesday, Baden-Clay revealed more details of the romance, including that the pair twice “had some physical intimacy” at his house, on the spare bed and on a spare mattress.

He said he was ultimately relieved when the relationship with Ms McHugh ended because he was ashamed of his behaviour.

The defence closed its case earlier on Wednesday.

The trial has heard evidence from more than 70 witnesses since it began just over three weeks ago.

Defence and prosecution counsel are expected to deliver closing addresses on Monday.