Workers from Chemist Warehouse in two states have gone on an indefinite strike over what they claim is a widespread culture of sexual harassment and labour exploitation.

Key points: Workers are demanding an end to alleged workplace bullying and sexual harassment

Workers are demanding an end to alleged workplace bullying and sexual harassment Chemist Warehouse distribution centre workers earn about 25 per cent below the industry standard

Chemist Warehouse distribution centre workers earn about 25 per cent below the industry standard The strike could affect the supply of retail items, but medicines will not be impacted

The workers from the retail pharmacy chain gathered outside the company's distribution warehouse in Preston, in Melbourne's north, to announce the industrial action, which is also taking place at the company's storehouses in Somerton, Victoria as well as Eagle Farm in Brisbane.

Workers at the warehouses are demanding higher wages and an end to what they say is job casualisation and sexual harassment.

Up to 800 staff and casual workers across the three sites have joined the fight.

The workers ship approximately one million retail items a week, and it is expected there will be a significant impact on retail stock supplies within days.

However, there will be no impact on medicine supplies.

Anger over workforce casualisation

About 70 per cent of the pharmacy retailer's Victorian warehouse staff are labour-hire casuals.

The National Union of Workers (NUW) said both permanent and casual staff earned approximately 25 per cent below the industry standard.

The union's national secretary, Tim Kennedy, said labour-hire casuals received text messages, sometimes as late as 10:00pm, notifying them of their shifts the next day.

"It's a model that basically keeps people in fear, they can't plan their lives," Mr Kennedy said.

"There's a lot of downtrodden, exploited people in this place and for them to take a stand today, to come out on strike, is a big leap in hope and courage — and we need to stand with them."

Warehouse worker and NUW union delegate Husain AlQatari also said casualisation left workers vulnerable.

"It's an unsecure job, an unsafe work environment, it's low wages," Mr AlQatari said.

"How can people, like a labour hire worker, live on one day or two days a week — sometimes even one day a fortnight — with $24.25 an hour?"

The union claims there have been multiple allegations of sexual harassment at the company, with the NUW recently submitting employee statements to the National Inquiry into Sexual Harassment in Australian Workplaces, headed by the Australian Human Rights Commission.

"The workers, if they speak up, it's a private investigation," Mr Kennedy said.

"They don't know what the outcome of the investigation is, it's never resolved, and too often people who do raise these allegations lose their work."

The union said it had been investigating Chemist Warehouse for almost two years.

In the lead-up to the strike last week, several sit-in protests took place at Chemist Warehouse stores in Victoria and Queensland.

The ABC contacted Chemist Warehouse for comment.