Job cuts by the National Trust for Scotland (NTS) may leave the organisation less than viable, the national secretary for trade union Prospect has warned.

Speaking out following the trust's announcement that it would scale down its planned redundancies from 91 to 65, Alan Denney said: "It is welcome news that fewer people are being forced out of work on a compulsory basis.

"But when you dig beneath the surface, as well as the 65 redundancies, 44 of which are compulsory, there are a number of seasonal staff cuts and approximately another 50 vacancies that the NTS will not be filling.

"So somewhere in the region of 150 jobs have gone. Out of a total of 490 jobs, there is a concern that a less than viable organisation remains."

Kate Mavor, chief executive of the NTS, said: "While it is fair to say that, like many organisations, we are facing challenges at the moment, we are making good progress in strengthening our finances and we anticipate that we will be in surplus by the end of this year."

Denney also claimed that NTS's financial problems were due, in part, to a disproportionate emphasis on fundraising for a £21m museum dedicated to the poet Robert Burns. The NTS took over the site in November and the museum is expected to open next year. Mavor refuted this suggestion.

"Claims that the Robert Burns Birthplace Museum project is putting the charity under too much pressure are unfounded," she said. "In fact, we believe that this important work is critical to the trust's future."

As Museums Journal went to press, the NTS was also resisting calls by In Trust for Scotland, a breakaway group of disgruntled NTS members, for an extraordinary general meeting to be held at the trust's annual general meeting in September, to discuss its financial situation and the thinking behind the closure of several NTS properties.

An NTS spokeswoman said the trust had not yet received the required number of signatures to call an extraordinary general meeting.