Stewart Dickson MLA said: “Attacks on the constituency office of any political party are unjustifiable and an assault on the entire democratic process.
“Those working in constituency offices deserve the same rights as everyone else in Northern Ireland – to be able to go to work without fearing for their safety.
“Democracy must prevail. Those who attack the offices of elected representatives do so with the aim of pulling Northern Ireland back to the dark days of the past – but their efforts cannot succeed.
“I would appeal to anyone with information to contact the PSNI immediately. Public representatives should be able to provide constituency services free from threats and intimidation.”