The owners of a mansion in Midlothian are planning legal action against organisers of an “utterly irresponsible” party attended by more than 300 people in their rental property last weekend. Police Scotland pleaded with the public to take personal responsibility after revealing that officers attended more than 300 house parties across the country last weekend. The coronavirus transmission rate in Scotland has increased above 1 in the past seven days. The owners of the Mansion House at Kirkhill, near Gorebridge, said they were devastated to discover that their former family home was being used for a “huge rave”, after receiving a call from concerned neighbours early last Sunday morning. They said: “We utterly condemn both the organisation and people behind this but also those that turned up to this so-called party. Knowing the current laws that are in place to keep us all safe and healthy, I am shocked that anyone would put others in danger to do this.” They said they had accepted a reservation request for a family gathering of 10 people, including three children, for the property, which is marketed across a number of platforms, including Airbnb, as a “private and peaceful” venue for weddings and birthday parties. Scotland’s first minister, Nicola Sturgeon, condemned the event for “threatening our progress out of lockdown”. She tweeted: “It’s hard to put into words how utterly irresponsible this kind of behaviour is in current circumstances. It puts people at risk and threatens our progress out of lockdown. PLEASE do not attend house parties just now.” On Thursday, Sturgeon said house parties “were still a concern”, but that smaller gatherings were also believed to be driving the clusters in the west of Scotland that resulted in Tuesday’s decision to increase local restrictions on people meeting indoors in private houses for the following two weeks. On Friday afternoon, 159 new cases of coronavirus were confirmed in Scotland, 73 of them in Greater Glasgow and Clyde, where the indoor gathering restrictions are in place across three local council areas. Lanarkshire’s public health director warned residents could be facing similar restrictions after a rise in the number of cases there. Speaking on BBC Radio Scotland on Friday morning, the Police Scotland deputy chief constable, Malcolm Graham, said that while the force had sympathy in particular with younger people whose freedoms were being curtailed, “this is a plea to people for the weekend ahead to continue to take personal responsibility, as the vast majority of people are”. On Thursday, Police Scotland confirmed that the organisers of the ticketed party could face charges of culpable and reckless conduct. Officers arrived at about 12.20am on Sunday to disperse the crowds. A 29-year-old man was issued with a fixed penalty notice at the time. Graham said the force had handed out 10 similar fines across the country since new powers to break up parties of more than 15 people came into force last Friday. Stephen Curran, the chair of Midlothian council’s police and fire and rescue board, described the partygoers as “selfish and irresponsible”. He said: “Those 300 or so people didn’t just put themselves at risk of contracting coronavirus, they put residents across Midlothian and beyond at risk.”