Australian unions have been allowed back into the Abbott government's budget lock-up, after initially being given only three seats.

As reported last week, only the Australian Council of Trade Unions had been given access to the stakeholder budget lock-up and had just been allowed three spaces rather than their usual five.

At the time, ACTU president Ged Kearney said it was a blatent attempt to cut unions out of the first round of analysis of a budget which would hurt union members.

The union movement has since been given access to the lock-up, albeit in smaller numbers than usual.

The ACTU has been given a number of additional seats in the stakeholder lock-up by the federal government, two of which went to the Australian Services Union and the Community and Public Sector Union.

ASU NSW/ACT secretary Sally McManus said they had been allocated one spot in the stakeholder lock-up, after they raised concerns about being refused entry.

"We had originally requested three spots," she said.

"One spot is definitely better than being locked out. Given the potential impact this budget will have on the community services sector, it's important that workers are represented."

Ms McManus said there were 41 programs funded by the federal government, which were on the union's watchlist for potential cuts.

"Whether we can serve the interests of our members via this process depends on the information provided to our representative in the lock-up," she said.

The CPSU, which represent the thousands of Canberra public servants possibly facing the knife in Tuesday's budget, said they had also been granted one place in the lock-up.

The Australian Manufacturing Workers Union said it had been offered two places in the media lock-up, rather than the stakeholder's event.

"We have accepted in order to read the budget papers. We were declined places in the stakeholder lock-up," a spokesperson for the AMWU said.

"Although not perfect, we are pleased that we will be able to read the budget papers on the day and know what is in store for our members."

The spokesperson said the AMWU  were offered the places the evening after their media release raising concerns went out, but they were unsure whether there was a correlation.