Bòrd na Gàidhlig said the resource spending review made no reference to the language, adding: "This is a significant omission.
"The result is a lack of clarity and transparency on the degree of future priority of – and funding for – Gaelic.”
The spending review, which was published in May, sets out the Scottish Government’s broad spending plans up to 2026/27.
It caused controversy after outlining more than £1 billion of real-terms cuts for key areas, including councils and the police.
Bòrd na Gàidhlig said neither the review nor its associated documents made reference to “Gaelic, its role as an economic asset and how it can contribute to the recovery”.
In a submission to Holyrood’s Covid-19 recovery committee, which is carrying out a scrutiny exercise before the Scottish Budget later this year, it said: “There is no case for any reduction in funding for Gaelic.
"Rather, there is a case for increased funding to reflect Scottish Government policy, growing demand for the Gaelic language and culture, and Gaelic’s increasing contribution to Scotland’s economy.”
The body said 87,100 people in Scotland had Gaelic skills at the time of the 2011 census, of which 57,600 were speakers.
About 50 per cent of these speakers lived in the Highlands and islands.
Meanwhile, across nursery, primary and secondary schools, the number of pupils in Gaelic-medium education grew from 4,328 in 2011/12 to 6,272 in 2020/21 – an increase of 45 per cent.
A 2014 report found the potential value of Gaelic as an asset could be up to £149 million, but Bòrd na Gàidhlig said this figure was “arguably conservative”.
It said the Scottish Government’s Covid recovery strategy, published last year, was “not adequately reflected” in the resource spending review document.
Meanwhile, “island” received only one mention in the strategy document, Bòrd na Gàidhlig said.
The organisation added: “These points mean there is reduced confidence that issues identified in the strategy will be reflected in the outcomes from the resource spending review.”
The body also said there was no reference to geographic barriers, adding: “This does not give confidence that it will be adequately addressed.”
It pointed to the general economic fragility of many island and rural areas and the relatively high share of businesses in sectors “disproportionately affected by the pandemic”, as well as high levels of self-employment.
The body said the cost of living was also higher in remote areas, adding: “These geographical aspects of the pandemic are not acknowledged in the resource spending review document, nor in the supporting ones. This is a significant omission.
“Funding needs to reflect the extent to which the economies of remote and island communities were hit by the pandemic. This will support the sustainability of these communities.
"That is vital because the Gaelic language is not only important to these remote areas and islands, but their sustainability is essential to the continued sustainability and growth of the Gaelic language.”
A Government spokeswoman said: “Gaelic is significant part of Scotland's culture and this Government is committed to see it thrive and grow, which is why we have continued to grow the budget in recent years.
“We recognise the value of the language to Scotland’s economy and that is why the Cabinet secretary for finance launched a short-life working group on economic opportunities for Gaelic. It is expected that this group will report back in the autumn.
“In addition, we launched a national consultation last week aimed at ensuring a robust future for the language.”