CCTV footage shows the pair break into the property in Ashgill Road, Milton, on Saturday at about 20:15 and attempt to set light to the door.

Police said the blaze did not take hold because of the wind and rain.

They returned at 22:10 and broke into the office before setting another fire which caused substantial damage.

Det Con Katy Allan, of Police Scotland, said: “We know from our enquiries that this was a targeted attack.

“The men, who had been sitting in a silver car opposite the building for some time prior to the incident, had the audacity to come back and set a fire again when the first one didn’t take full hold.

“They were obviously determined to inflict some serious damage to the building which will now be closed until enquiries and repairs are complete.

“As mentioned, the men had the engine running in the car prior to the fire and I am sure they would have been heard or seen by a neighbour for this reason.

“Anyone with information about the fire raising can contact Maryhill CID on 101 or alternatively can call Crimestoppers on 0800 555 111 where details can be given in confidence.”

GHA North West Area director, Jackie Morris, said: “We’ll re-open our Milton office as soon as possible. In the meantime, tenants can use a couple of other GHA offices nearby.

“We are co-operating with the police as they investigate the fire.”

@GlasgowHousing