The numbers are from The Bombers and the Bombed by Richard Overy
"By the time Italy declared war on June 10th "Haddock force" as it was known, had operational bases, fuel, and supplies on two southern French airfields. On June 11 a dozen Wellington bombers arrived, but the French military authorities were now opposed to any bombing of Italy that might provoke retaliation against French cities, and they parked trucks on the runway to prevent takeoff. Only after days of inter-Allied argument did a force of eight aircraft set off on the night of June 15-16 to bomb the port of Genoa, but only one found it; the following night six out of nine managed to locate and bomb Milan."
"Then the order came to evacuate following the French surrender..."
"Only on the eve of armistice between France and Italy did French aircraft attack Italian targets in Sicily on June 23 and 24. killing 45 people in a gesture of pointless defiance." 
" The first raids on northern Italy carried out by Bomber Command from British bases in June and August 1940 - three in all involving only seventeen aircraft- were reported to have "a 'stunning' effect on Italian morale."
"Since Italy was difficult to reach from British bases or from bases in Egypt with existing aircraft, heavy bombing was not yet an option. But since Italy was regarded as politically fragile, a leaflet war was mounted to try to persuade the population to give up the fight."
"a total of 4,780,500 leaflets were dropped between 1940-1942…"
"Nothing in the end came of the political initiative, and the bombing was in reality small scale and intermittent, a "small switch", as Charles porter put it, rather than "a big stick."
Throughout 1940 and 1941 there were twenty- four small raids by Bomber Command (only four of them in 1941) and ninety-five raids from Malta, most of them by hand-fuls of Wellington bombers, seldom more than ten at a time, on their way to bases in the Middle East." 
In November 1940, for example, six Wellingtons attacked Naples, where they reported a poor blackout, no searchlights or enemy aircraft, and inaccurate antiaircraft fire."
" A raid on Taranto by ten Wellingtons on November 13-14 could be carried out from 5,000 feet because there were once again no searchlight, aircraft, or barrage balloons, and inaccurate gunfire. The blackout was poor in all areas and trains could be seen running between towns fully lit."
"In October 1941 the Foreign Office suggested that at the right moment, when Italian morale was judged to be cracking, a heavy bomb attack might prove to be a "knock-out blow" but Portal insisted that the war in Libya took priority."
"In the first nine moths of 1942 there was only one Bomber Command raid in Italy, in April against the Savona on the Ligurian coast, and thirty-four small raids from Malta against airbases and ports despite the Axis bombing of the island. For most of the period from late 1940- to the late autumn of 1942, much of Italy was spared anything more than damaging nuisance raids."
More from Pg. 322
"in the last two months of 1942, six area raids were made on Genoa, seven raids on Turin, and one daylight raid against Milan. There was negligible resistance to the daytime raid, by eighty eight Lancastors, and bombs were released over Milan from as low as 2,200 feet, though the post raid report indicated that there had been too few incendiaries dropped to cause the kind of fire damage common in air attacks on Germany. Indeed detailed research by the RE8 department for the air ministry showed that Italian architecture was less prone to either lateral or verticle fire damage than German because of the extensive use of stone and marble, solid stone flooring, the thicken mass of the walls and the wide courtyards and streets. RE8 recommended dropping high explosives..."
Pg. 323 describes Italian AA defenses & pg. 324 starts getting into 1943 bombing.
 Stephen Harvey, "The Italian War Effort and the Strategic Bombing of Italy," History 70 (1985);:38.
 TNA, AIR 20/283, Air Ministry, notes on bomb attacks, August 20, 1940.
 TNA FO898/457, PWE, "Annual Dissemination of Leaflets by Aircraft and balloon, 1939-1945.
 TNA, AIR 2/7397, Air Ministry to HQ Middle East, September 5,1941.
15] TNA, AIR 23/5752, Wellington Operations from Malta; Marco Gioannini and Giulio Massobrio, Bombardate L' Italia: Storia della guerra di distruzione aerea, 1940-45 (Milan; Rizzoli, 2007) online appendix.
 TNA, AIR 2/7379, HQ RAF Med to Bomber Command HQ, November 1,1940; HQ Malta to HQ Middle east, November 14, 1940; HQ Malta to HQ middle East, November 23, 1940.
 TNA, AIR 8/436, Cadogan ( Permanent Secretary, Foreign office) to Portal, October 21,1941; Portal to Cadogan, October 26, 1941.
 TNA, AIR 2/ 7397, Cadogan to Freeman (DCAS, January 8, 1942; Freeman to Cadogan, January 9, 1942
 Ibid., reports on raids in October and November1941 classified nine of the sixteen raids as nuisance raids, using fewer than seven aircraft. on British policy see Baldoli and Knapp, forgotten blitzes, 20-21,25