Unless the white lines were painted by your neighbour, they are the responsibility of your local council. Strictly speaking they have no legal standing and are officially termed 'access protection markings', so it is most likely that your neighbour has paid to have the lines painted outside the house.

We would suggest contacting your local council to request information on the installation of the lines and to see if they can be altered so they are not encroaching outside your house. You do of course have the option to park on them regardless, or you may wish to politely discuss the matter with your neighbour before contacting the council to avoid any possible disagreements.