Unions fear Qantas is preparing to sack 3,000 workers and then re-employ them through company-controlled labour hire firms and subsidiaries on lower wages and conditions, as part of a deal to win federal government assistance.

Responding to reports that it would cut the 3,000 jobs when it announces its half-year results next Thursday, Qantas issued a statement late on Friday saying it had already "flagged the need to make tough decisions as part of strengthening our business" including at least 1,000 job cuts over the next 12 months. It said it would not be reducing its services to London.

The airline has said it will cut $2bn from its operating costs as it pleads with the federal government to offer some form of debt guarantee or assistance to help it compete with rival carrier Virgin, which is backed by foreign government-owned airlines.

The Transport Workers' Union national secretary, Tony Sheldon, said the union believed Qantas was preparing to terminate around 3,000 workers at one of its divisions and then rehire them through subsidiary companies.

"It is really a sham outsourcing arrangement. They terminate a contract with themselves to give the appearance that the jobs are going to a new business … It's all part of the deal they have done with the federal government to win assistance," Sheldon claimed.

In January Qantas "axed" flights to Tasmania and 35 jobs at Hobart airport, with the routes taken up by Qantas regional brand Qantaslink, which immediately began to recruit new ground handling staff.

In a statement at the time, Qantas said the overall level of direct and indirect employment in Tasmania would increase.

The government is considering offering Qantas a "standby" or emergency debt guarantee after two ratings agencies downgraded its credit rating to "junk" status. The move would not require legislation.

The company, and some Coalition backbenchers, have been lobbying for changes to the Qantas Sale Act to remove the requirement for majority Australian ownership and allow foreign investors to hold more than 49%. The prime minister, Tony Abbott, and the treasurer, Joe Hockey, have said this is the best available option.

But the Labor party and the Greens have ruled out support for the amendment in the Senate, meaning it could not pass parliament before the new Senate sits in July. And Clive Palmer, whose Palmer United party senators will hold crucial crossbench votes after July, has also ruled out supporting the change.

In a speech to Coalition backbenchers two weeks ago, the Qantas chief executive, Alan Joyce, acknowledged that neither a direct cash injection by government nor legislative change was possible.

"We have never asked for a handout. And we are not asking for one now … The Qantas Sale Act limits our financial options, it adds cost to our business and it influences our actions as a publicly listed company. Over the long term, repealing it is essential to remove the distortions in our aviation system. However, we recognise there is little political and community appetite for changing the act in the short-term," he said.

The government has said it will make a final decision about a debt guarantee for Qantas after the airline's profits announcement.

The guarantee could mean ratings agencies would classify the airline as a government-related entity, allowing it to regain an investment-grade credit rating and reducing the cost of its borrowings. But should the airline ever call on the guarantee it would be required to pay a substantial fee.

Virgin has reacted angrily to the proposal, saying it would immediately ask the government for the same deal as anything offered to Qantas.