Dozens of port workers have formed a picket line at a wharf at Port Botany in Sydney after 97 workers from Sydney and Brisbane were sent text messages telling them not to turn up for their shifts, and to check their emails.

The emails, sent by Hutchison Ports, said their positions had been made redundant, there were no re-deployment opportunities and their personal belongings would be couriered to them.

Workers still rostered to work on Friday joined their sacked colleagues on a picket line outside the terminal in Port Botany.

Opposition Leader Bill Shorten offered his support and visited the angry workers on the picket line outside the Hutchison Ports terminal.

The Hutchison gates are being blocked by hired security guards and trucks are having to turn away instead of delivering their containers.

An altercation flared after a security guard apparently told a sacked worker he could not enter and that his gear would be cleared from his locker and sent to him.

Extra police intervened to keep the security guards and picketers away from each other while border security officers kept a watchful eye.

Crane driver team leader Craig Hancock said he was yet to tell his family he had been sacked.

"I've got three kids and a wife and a mortgage," he said.

"I don't know what we're going to do, like everybody, very sad."

Shift leader Paul Wallington has been in the industry for 18 years and said it was devastating to receive the text message and email last night.

"It's looking bleak at the moment...my wife's upset, my kids are upset...it's going to be tough," Mr Wallington said.

"Today's the first day and I don't think it's going to get any better unfortunately."

Sacked wharf worker Martin O'Daly said he has a wife, a mortgage and has just bought a new car. ( ABC News: Deborah Rice )

The maritime union said the 97 employees - 40 in Brisbane and 57 in Sydney - were sacked by an email sent at midnight.

In the email, the company blamed the redundancies on a number of issues including the downsizing of its offerings to Australian customers.

New South Wales assistant branch secretary Paul Garrett said the union rejected that claim.

"It's clear that the company's got a move to automate and this is just one of the steps along the way to automating but there shouldn't be any automation without negotiation and they certainly should enter into meaningful discussion with the workers and their union, not just sack them at midnight," he said.

Holly Mathewson, a stevedore, said she was the first female employed by the company.

"[I'm] shattered. My dad works here, my sister works here, we're all gone," she said.

"I was proud to be a female on the wharves and it just destroyed it.

Holly Mathewson, who said she was the first female employed by the company, joins her colleagues at the picket line. ( ABC News: Deborah Rice )

"I've been here since it was dirt, helped build the place and this is what they do."

Martin O'Daly a maintenance shift leader, said he has a wife, a mortgage and had just bought a new car.

"I got the email turned over and spoke to my wife at 3 o'clock this morning, first thing she done was burst into tears crying," he said.

"If this company today get away with this, is this the sort of Australia we want to live in? It's just heart wrenching."

Mr Hancock claimed the company had earlier threatened to close down without notice.

"Bottom line is we bent over backwards, we tried our hardest we're a really good workforce...but they're trying to pick on us all the time," he said.

"They've got nastier and nastier...we don't really know why we've been sacked.

"They started threatening us a while ago about 'we'll close down whenever we like', or 'we'll make you redundant for no reason'... they kept saying stuff like that but we kept battling away.

"Then last night I get an email at 12 o'clock."

Hutchinson Ports has not responded to repeated requests from the ABC for comment.