A death threat has been sent to WA's Transport Minister Rita Saffioti in a letter mailed to her Perth home and opened by her eight-year-old daughter, a day after fellow Labor MP Tony Buti was sent a similar letter.

Key points: Letters containing death threats were sent to Rita Saffioti and Toni Buti a day apart

Letters containing death threats were sent to Rita Saffioti and Toni Buti a day apart The threats relate to the WA Government's taxi reforms, the Premier says

The threats relate to the WA Government's taxi reforms, the Premier says Police are putting additional security arrangements in place for both MPs

The WA Government said the letter, which arrived at Ms Saffioti's address on Tuesday, was accompanied by death notice clippings of her father, who recently passed away.

Premier Mark McGowan confirmed both letters related to the Government's proposed reforms of the taxi and ride-sharing industry and made demands for a different arrangement.

He said the letter to Ms Saffioti also threatened the lives of her family, which includes three children.

The letter to Dr Buti, the member for Armadale, reportedly threatened "strange things will happen to your family" unless he "fixed the taxi industry".

Tony Buti has been helping Ms Saffioti with Labor's transport reforms. ( ABC News: Jacob Kagi )

Dr Buti has been assisting Ms Saffioti with the State Government's taxi and ride-sharing transport reforms ahead of new laws being introduced to the WA Parliament today.

Police are understood to be investigating the threats against both Ms Saffioti and Dr Buti.

"This is one of the most disgraceful and appalling things I've seen in my political life, that someone would threaten another person's children," Mr McGowan said.

"If people think that in some way it will get them the outcome they want, they are completely wrong.

"That's not the way that we work in Western Australia, that's not the way government works in Australia."

Police boosting security for MPs

Mr McGowan said there would be "very serious consequences" for those who sent the letters if they were caught.

The Government's proposed taxi and ride-sharing reforms have angered some in the industry. ( ABC News: Andrew O'Connor )

He said Ms Saffioti was coping pretty well in the circumstances, adding "she's a strong personality".

The Premier said police were putting additional security arrangements in place for both Ms Saffioti and Dr Buti.

Under the Government's proposed reforms of the taxi industry, plate owners would receive a maximum of about of $250,000 under a buy-back scheme.

The changes would see a 10 per cent levy imposed on all metropolitan trips to pay for the scheme.

The Liberal Party and key crossbenchers vowed to oppose the controversial so-called "Uber tax" after the plans were initially unveiled last November.