Abstract: In this thesis, I discuss a new statistical method to search for tidal streams generated by globular clusters. This method has been applied to the Gaia Data Release 2 catalogue detecting two new tidal streams generated by M68 (NGC 4590) and NGC 3201. The same method has been used to study the stellar stream of Palomar 5. These three streams are used to constrain the shape of the dark halo of the Milky Way within 20 kpc from the Galactic centre. I focus the analysis on the shape of the dark matter halo out of the plane of the disc, in particular, I study the halo density axis ratio. The three streams together favour a moderately prolate dark halo compatible with a spherical shape. This result is compatible with previous studies using stellar streams but is in tension with cosmological simulations that predict oblate halos for Milky Way-like galaxies. I will discuss this tension and the possibility of including more constraints to better describe the dark matter distribution around the Galaxy.