Governments are keen to say that they want to stop tax avoidance but in practice do the opposite.
In 2013, I visited the Dublin financial district (a well-known tax haven) and saw that BT and State Street (the company appointed by the UK Government to administer Auto Enrollment pensions ) both had a presence in that City. This is despite no publicity in the UK press nor on the BBC. HSBC a UK based bank also had an office there but did no banking and did not even have a branch in the whole of the Irish Republic.
The HMRC has completed a sale and leaseback deal on all its buildings through an entity called MAPELEY STEPS, based in Bermuda and numerous UK companies like Tesco PLC, Guardian Media Services, Daily Mail and General Trust have complex tax arrangements and are donors to the Conservative Party and the Labour Party respectively.
Getting global agreement on tax avoidance is well nigh impossible, so the answer is to follow the example of Singapore which keeps taxes low enough to avoid the worst excesses and runs the most efficient Government in the world with properly enforced laws and low levels of corruption and waste.