Speaking before the start of the G8/20 meeting, David Cameron said he wanted to focus on a small number of key priorities (Report, 25 June). He could make a good start on what should be a top priority – the latest damage being done to the world by the oil industry. Industrialised countries spend billions every year to support gas, coal and oil companies. The Gulf of Mexico spill shows the devastation these industries cause, but firms like BP are also ruining huge areas of wildlife habitats in Canada, right under the noses of Obama and Cameron. Every barrel of oil extracted from the Alberta tar sands creates four barrels of polluted water and creates as much as five times the greenhouse gasses of a barrel of conventional oil. Huge areas of boreal forest wilderness have been transformed into enormous open-cast mines and toxic ponds large enough to be seen from space. Please, Mr Cameron, President Obama, stop subsidising this pursuit of the last few drops of oil. The clean technologies to replace oil already exist. You can make it happen.

Ben Ayliffe

Greenpeace UK

• Yes, it's right that certain development aid budgets are maintained (Letters, 24 June). But in most debates the overriding issue of population is ignored. Medical and other advances (death control) since 1950 have greatly increased life expectancies in the developing world, while the acceptability of birth control lags well behind. Egypt's population has gone from 22 million in 1950 to 80 million now and is projected to be 120 million by 2050; Sudan's is projected to almost double to 70 million; Ethiopia's to more than double from 83 million to 183 million; and Uganda's to treble from 32 million to over 100 million. All these nations are dependent on the waters of the White and Blue Niles. But it is difficult for "the west" to call for family planning without attracting accusations of neocolonialism.

So unless population is addressed properly by the countries themselves; and unless we can be sure that no such aid ends up as motorways to nowhere, presidential palaces, or enables other funds to be used for such purposes (eg in Malawi this year); or is siphoned off into Swiss bank accounts; or is used to prop up Orwellian nightmares such as Burma and North Korea; or to benefit countries such as India and China which have their own space and nuclear weapons programmes; or, just as importantly, is more than offset by terms of trade which give greater benefits to the donor countries (eg Spanish fishing fleets ruining West African fishermen's livelihoods) – we might recall the conclusion of the development expert Professor Peter Bauer over 40 years ago that aid was "an excellent method of transferring money from poor people in rich countries to rich people in poor countries".

John Birkett

St Andrews, Fife