At least eight groups, many of whom have been long-time attendees, have confirmed they were told there wasn't enough room for them at this year's stakeholder lock-up.

One organisation was told the Treasurer's office and the Department of Treasury had chosen a list of stakeholders most relevant to the year's budget measures, while others were told the event had moved to a smaller space.

Australian Council of Social Service boss Cassandra Goldie slammed the decision as "arrogant and undemocratic", with many organisations offended and confused that they had been deemed less relevant, and left wondering if business and industry groups had faced the same rejections.

National Shelter, Early Childhood Australia, the National Foundation of Australian Women, Volunteering Australia, the Women's Electoral Lobby, and the National Aboriginal and Torres Strait Islander Legal Services are among community groups who had attended the lock-up previously and have this year found themselves locked out.

Other organisations have also been told they can't attend this year, but were wary of media reporting affecting their relationship with the government.

Cheryl Axleby, co-chair of National Aboriginal and Torres Strait Islander Legal Services, said the organisation had previously been invited, but had been excluded this year while budgets cuts loomed.

"We’re holding our breath for this year’s budget as we desperately need an injection and at least the $10 million of cuts to Aboriginal and Torres Strait Islander Legal Services projected in 2020-22 to be overturned," Ms Axleby said.

"Aboriginal and Torres Strait Islander people must be a priority or we will be forced to reduce front-line services resulting in Aboriginal and Torres Strait Islander kids, mums and dads going unrepresented and the disadvantage of our people will increase."

The National Family Violence Prevention Legal Services Forum, the only Aboriginal and Torres Strait Islander family-violence peak body, was told its convenor couldn't attend the lock-up, even though she had done so in previous years.

"Every year we wait for the budget with fingers crossed hoping we will be a priority," convenor Antoinette Braybrook said.

"This year we are told straight out we aren’t a priority and that we don’t align with budget measures.

"How can Aboriginal and Torres Strait Islander women not be a priority for the government given the disproportionate rates of family violence our women experience? This is shameful that we are not only told we aren’t a priority but that we can’t attend the lock-up to inform our members."

Many of the groups said they use the budget lock-up to prepare for media commentary, and to create documents summarising the budget for their stakeholders.

"There's lots of organisations and people who rely on us to give early advice on what the budget contains regarding housing, and that includes people in the lock-up," said Adrian Pisarski, executive officer for affordable-housing peak body National Shelter.

Mr Pisarski described the snub as "insulting".

Early Childhood Australia chief executive Sam Page said she now expects to spend a late night creating a budget summary for the peak body's members after the budget papers are released to the public at 7.30pm.

"It's not going to silence us," she said.

Ms Goldie said the decision as to which groups were included reflected the government's priorities, and contributed to a wider feeling of mistrust in politicians.

"There's a widely held view that the government has a gender problem, and then there's a whole lot of women's groups excluded," she said.

"One of the biggest debates we have is the lack of trust and confidence in government and politicians. The government needs to open up the doors to show it welcomes a diversity of voices, welcomes criticisms and is willing to listen."

In previous years the lock-up for stakeholders has been held at the Department of Treasury building, and in recent years at a larger venue at the Hyatt Hotel in Canberra.

A Treasury spokeswoman said the aim of the lock-up was to provide access for those "with a clear and immediate need", and there wasn't enough room for everyone who wanted to attend every year.

"The Treasury greatly values the contribution of community groups to the budget process," the spokeswoman said.

"They are generously represented in the budget lock-up, and attendees range from a variety of sectors, including disability, welfare, and mental health services."

Treasury said it couldn't provide lists of last year's and this year's attendees for security reasons.

Has your group also been excluded? Email sally.whyte@canberratimes.com.au.