The welfare effect of the existence of tax havens on high-tax countries has not been conclusive in the theoretical literature. Some papers show that the existence of tax havens is harmful to high-tax countries, while other studies argue that the opposite could occur. We aim to address a question: Do these welfare-reducing or welfare-enhancing properties still hold in the presence of lobbying? We find that the welfare-enhancing property does not hold, provided that the policy-maker attaches a sufficiently large weight to the political contribution received. Moreover, we point out that the cooperation among high-tax countries in restricting the international tax planning activity can lead to a lower level of social welfare in all high-tax countries.