Support for local shipping contractors is shaping up to become a significant issue in the Canning byelection, with the Labor candidate, Matt Keogh, signing a pledge on Monday to support the Australian shipbuilding industry and agitate for Western Australian companies to win federal contracts.

Keogh signed the bit of paper next to a collection of blue-collar employees from the Henderson shipyards of defence contractor BAE Systems, which has the maintenance contracts on a number of Australian navy vessels.

Workers at the union-controlled site say they are concerned about long-term job prospects, despite a large billboard at the entrance advertising that the company is hiring.

The Australian Marine Park shipbuilding precinct at Henderson, 37km south of Perth, is two electorates over from Canning, in the electorate of Fremantle, which is held by Labor’s Melissa Parke. But it is a major source of employment for Perth’s southern suburbs.

“This shipbuilding industry, and maintenance, is a critical way of us growing and continuing to maintain a manufacturing sector in Australia and Western Australia,” Keogh said.

“With the end of the mining boom we have got rising unemployment, we have got very high youth unemployment, people want to know where their next job is going to be, where they are going to have a sustainable job and where their kids are going to have a job.”

With lunch containers at their feet signalling that the meeting had cut into their meal break, eight employees of BAE Systems listened and then applauded as Keogh rubbished the commitments of Tony Abbott, who in August brought forward defence contracts worth billions of dollars in South Australia in an effort to revive the government’s political fortunes in that state.

The prime minister also guaranteed the majority of the shipbuilding work on those contracts would be done in SA, after the government retreated from an election promise to build a new fleet of submarines in South Australia. That contract will still be open to tender from international shipbuilders.

The defence minister, Kevin Andrews, said at the time the expedited contracts would end the “boom and bust which has occurred in terms of naval shipbuilding in this country”, which had led to a gap between contracts known among contractors as “the valley of death”.

It’s that boom-and-bust cycle that, according to the ABC, prompted BAE Systems to tell staff at its shipyards in Williamstown, Victoria in June that it would not bid for contracts to build the new patrol boats, putting 800 jobs at risk.

The shipyard workers also applauded the opposition workplace relations and employment spokesman, Brendan O’Connor, who raised the spectre of the China free trade agreement – a prominent motif in Labor’s campaign for the working-class seat – as a potential threat to Australian jobs.

“For my view, when you’ve got Aussies out of jobs, those people should be going as well,” one man in high-visibility cotton drill piped up.

Another was concerned about training opportunities. “We need more money put into Tafes so our kids can get apprenticeships and can get jobs here,” he said.

O’Connor said the Abbott government had let down the WA manufacturing industry by failing to “properly give undertakings to shipbuilders in this state.” He also said he would never talk down Australia’s shipbuilding industry, in reference to the comment by Liberal senator for WA and former defence minister, David Johnston, who said of government-owned shipbuilder: “ I wouldn’t trust them to build a canoe.”

But he wasn’t able to explicitly outline Labor’s promise to the shipbuilding industry – except to say that it had their support.

“Yes, we do need to at some point outline precisely those things and, as you say, in opposition that’s not as easy, but our guarantee is to ensure that shipbuilders and employers of shipbuilding have opportunities now and into the future,” he said.

“And we don’t believe the government has said anything other than what it had to say to provide support for a number of its own MPs in South Australia … We think it’s purely about politics, rather than a commitment to this industry.”

O’Connor said committing to building submarines in Australia would at the very least ensure the maintenance continued to occur at the Henderson shipyards in WA.

“This byelection is a referendum on jobs and a referendum on the record of this government to date, and I gotta tell you, the record has been pretty shabby up to this point.”

Monday marked two years since the Abbott government stormed to power in a landslide election win in 2013.

While Keogh was surveying shipyards, his main rival, Liberal candidate Andrew Hastie, was doorknocking houses in the south-eastern Perth suburbs of Armadale, Kelmscott and Roleystone, which make up the northern most part of the electorate.

Hastie is understood to have got some residents in Mandurah, the coastal city where he is basing his campaign, offside on Sunday, because a plane towing a “Vote 1 Andrew Hastie” banner spent several hours circling the suburbs. Hastie’s office confirmed the banner stunt.