A police officer who admitted assaulting his five-week-old baby has been sentenced to a 10-month community-based order by a Perth court.

Nickolas Wayne Peake, 30, faced Midland Magistrates Court today, having earlier pleaded guilty to assaulting his daughter at the family's home in Stratton last month.

The baby did not sustain any injuries.

The court heard she had been lying in her bassinet next to her father's side of the bed when she began screaming and crying around 11pm.

Peake picked up his daughter by her sleep-sack and tried to settle her.

But when he was unable to do so, he shook her back and forth three times and yelled "shut the f*** up".

Peake's wife immediately took the baby from him and he left the room.

'Betrayal of trust'

Peake claimed his memory of the incident was "a blur".

Magistrate Paul Lyons said although Peake's actions were "isolated and out of character", the risks they posed to his baby daughter were great.

"It's hard to imagine anyone more vulnerable to an offence of this kind,"he said.

"Acting the way you did represents a betrayal of trust, not just that your infant has put in you, but that which your broader family has put in you.

"Physical violence of this kind is utterly unacceptable and must be deterred."

Peake's wife had experienced a complicated birth with their daughter, enduring a 40-hour labour and blood loss, the court heard.

While Magistrate Lyons acknowledged Peake had been experiencing stress as a new parent, he said his experience of fatherhood was not unique.

"It strikes me the circumstances you faced are similar or the same as any other new parents," he said.

"And you, as does anybody facing this situation, need to learn to control yourself and deal with the stresses which come with being parent."

'Genuine remorse'

Despite this, Magistrate Lyons said a term of imprisonment was not appropriate.

"You acted in a protective manner after by taking your daughter to hospital and being frank with what happened," he said.

"You have been open and forthcoming with the Department of Communities.

"The [early] plea in this case is also reflective of genuine remorse for what happened and what you did."

The ex-homicide case manager's lawyer, Stuart Counsel, applied for a spent conviction to mitigate adverse consequences to his client's employment prospects.

"It is likely Mr Peake will lose his job over this and the significant media coverage will make future employment difficult," he said.

But Magistrate Lyons dismissed the application and ordered Peake pay $850 in costs.