More than 420 staff at the National Trust for Scotland (NTS) are at risk of redundancy.
The conservation charity has launched a series of emergency actions after it said its future was in doubt.
A total of 429 staff in the organisation’s permanent workforce are at risk of redundancy.
NTS has also said it will look to sell off non-heritage land and property, and seek support from the Scottish government and grant-giving bodies.
The trust, which looks after places such as Culloden, Culzean Castle and Hill House in Helensburgh, said its income had been virtually eradicated during what was normally its busiest period.
The charity’s estate and holiday accommodation has been closed since March to comply with the coronavirus lockdown restrictions.
NTS said its income was forecast to drop by £28m this year and said it had also made investment losses of £46m due to stock market conditions.
‘Impoverish Scotland forever’
Chief executive Simon Skinner said: “The extreme and unprecedented public health emergency has put the charity’s future in doubt.
“With some level of restrictions likely to apply post-lockdown and having effectively missed the busiest part of the visitor season, I see little prospect of us being able to return to more normal levels of membership, visitation and income for the rest of this year and beyond.
“Some people may not care that a charity is in trouble or see heritage as having little importance just now – but if the trust goes down then what will be lost will impoverish Scotland forever.”
The trust, which currently has 751 employees, plans to scale back its offering based on the possibility of a staged reopening of 27 key properties this year on a limited basis.
The remainder will be placed on a “care and maintenance basis”, with the aim of opening a further 18 sometime next year, and the rest once there is a general upturn in the economy and the trust’s fortunes.
David Avery, of the Prospect trade union, said: “This is a huge blow to workers at National Trust Scotland who will be extremely worried about their futures.
“We will do all we can to support members and argue strongly for the retention of jobs.
“Prospect will be seeking assistance from the Scottish government to protect jobs and help keep staff in place at these important historical landmarks which will be so important to Scotland’s tourism and cultural sectors as we recover from Covid-19.”