If 1hp~746W we are talking about 1150 to 2300W.. There are variable speed boxes for drills and similars, but do not know if they support that power.
If you do not find it, maybe a lamp dimmer with support for the Watts your motor eats could work, but again do not know if they exists for that power.
If you do not find it you will need any AC voltage regulator with a triac able to support at least 2300W/220V=10.45A. The SM12J45 triac for example is able to drive 12A of AC.
hope it helps