Windows have been smashed at the workhouse before

Dyfed-Powys Police said "numerous windows", fire extinguishers and a mail box had been damaged at the Grade II-listed Y Dolydd in Llanfyllin.

A team trying to save the building is in a race against time to repay a �340,000 loan used to buy it in 2005.

In 2004, the workhouse, built in 1838, featured in the BBC Restoration series.

Dyfed-Powys Police in Llanfyllin, near Welshpool, said the damaged caused to the old building was "undermining" the efforts of the charitable trust trying to restore the property.

Nina Wehling of the Workhouse Group, which joined forces with the trust last year, said: "The damage has been caused at night over the last three weeks.

The workhouse was built in 1838

"Windows have been smashed and doors have been kicked in. It's a bit demoralising when we're trying to save the building to find that it's being damaged."

Ms Wehling added that windows had been damaged there in the past.

The group has given itself until 31 July to raise the �340,000 to repay a loan from the Architectural Heritage Fund, otherwise the workhouse may be sold for housing.

But the group is hopeful it will succeed and on 29 June it holds its annual three-day Workhouse Festival, a showcase for up and coming bands, where it hopes to raise money.

Organisers said the event was already a sell-out having already sold 4,000 tickets.