A method for the combined perforation and cleaning of annuli (6, 8) in a well over a longitudinal section of the well and subsequent plugging of the longitudinal section; the well being provided with, at least over the longitudinal section to be plugged, at least two pipe bodies (5, 7) placed substantially concentrically, including an innermost pipe body and an outermost pipe body, the method including the following steps: lowering a perforation tool into the innermost pipe body to said longitudinal section of the well; forming perforations (51, 71) in the at least two pipe bodies (5, 7) along the longitudinal section by means of the perforation tool, characterized in that the method also includes the steps of: by means of a flushing tool, which is attached to a lower portion of a string allowing through-flow, and which is lowered into the innermost pipe body to the longitudinal section, pumping a flushing fluid down the string, out through at least one outlet of the flushing tool, into the innermost pipe body and further out via said perforations (51, 71) into said annuli (6, 8) comprising an annulus located between the at least two pipe bodies (5, 7) and an annulus located outside the outermost pipe body; pumping a fluidized plugging material down the string and into the innermost pipe body at the longitudinal section; and placing the fluidized plugging material in the innermost pipe body, and thereby also in said annuli (6, 8) via the perforations (51, 71) in the at least two pipe bodies (5, 7), along at least said longitudinal section of the well, whereby the at least two pipe bodies (5, 7) and said annuli (6, 8) are plugged along at least said longitudinal section of the well; and - wherein the flushing tool used in step is formed with a plurality of outlets allowing through-flow; - wherein at least one of said outlets is angled in such a way that the output jet is non-normal to a longitudinal axis of the flushing tool; and - wherein the outlets are angled in such a way that the output jets are distributed within ± 80° from a plane which is normal to the longitudinal axis of the flushing tool. lowering a perforation tool into the innermost pipe body to said longitudinal section of the well; forming perforations (51, 71) in the at least two pipe bodies (5, 7) along the longitudinal section by means of the perforation tool, by means of a flushing tool, which is attached to a lower portion of a string allowing through-flow, and which is lowered into the innermost pipe body to the longitudinal section, pumping a flushing fluid down the string, out through at least one outlet of the flushing tool, into the innermost pipe body and further out via said perforations (51, 71) into said annuli (6, 8) comprising an annulus located between the at least two pipe bodies (5, 7) and an annulus located outside the outermost pipe body; pumping a fluidized plugging material down the string and into the innermost pipe body at the longitudinal section; and placing the fluidized plugging material in the innermost pipe body, and thereby also in said annuli (6, 8) via the perforations (51, 71) in the at least two pipe bodies (5, 7), along at least said longitudinal section of the well, whereby the at least two pipe bodies (5, 7) and said annuli (6, 8) are plugged along at least said longitudinal section of the well; and - wherein the flushing tool used in step is formed with a plurality of outlets allowing through-flow; - wherein at least one of said outlets is angled in such a way that the output jet is non-normal to a longitudinal axis of the flushing tool; and - wherein the outlets are angled in such a way that the output jets are distributed within ± 80° from a plane which is normal to the longitudinal axis of the flushing tool. - wherein the flushing tool used in step is formed with a plurality of outlets allowing through-flow; - wherein at least one of said outlets is angled in such a way that the output jet is non-normal to a longitudinal axis of the flushing tool; and - wherein the outlets are angled in such a way that the output jets are distributed within ± 80° from a plane which is normal to the longitudinal axis of the flushing tool.