British Prime Minister David Cameron on Monday called for joint efforts to tackle tax evasion and aggressive tax avoidance weeks ahead of the Group 8 (G8) Summit to be held next month. In a letter written to leaders of crown dependencies and overseas territories, Cameron said he had made the fight against tax evasion and aggressive tax avoidance a priority for the G8 Summit, adding that it was the \"critical moment to get our own houses in order.\" The summit is scheduled to open in North Ireland on June 15. The letter is written to Britain\'s ten overseas territories, including some of the world-known \"tax heavens.\" The prime minister welcomed the commitments those overseas territories made earlier to automatic tax information exchange, both on a bilateral and multilateral basis. He said the move would \"help us to reach our goal of setting a global standard in tax transparency.\" \"But dealing with tax evasion is not just about exchanging information. It is also about improving the quality and accuracy of that information,\" Cameron said in the letter. \"Put simply, that means we need to know who really owns and controls each and every company. This goes right to the heart of the ambition of Britain\'s G8 to knock down the walls of company secrecy,\" he wrote. He urged the territories to sign international agreements designed to allow tax information to be shared more easily between countries. In an early interview with a U.S. media, Cameron disclosed the agenda of the G8 summit meeting, which includes increasing trade, fairer taxes and greater transparency. He expressed his hope that the overseas territories could seize the opportunity to showcase progress on tax, trade and transparency they together have made, and set the global standard on transparency. \"We also need to ensure information exchange works effectively for all, particularly the poorest countries in the world. That is why we strongly support the Multilateral Convention on Mutual Assistance in Tax Matters,\" the British prime minister said.