If you want to understand how half the countries that still criminalise homosexuality came to do so, look no further than the British Empire. The list of 84 jurisdictions across the world, compiled by the newly formed Human Dignity Trust (HDT), includes 42 Commonwealth countries, or 80 per cent of the Commonwealth community.

Almost all imported British laws in place in the late nineteenth century that, at that time, outlawed homosexual acts. It took until the 1967 Sexual Offences Act before England and Wales repealed its own legislation and until the 1980s before Scotland and Northern Ireland did the same. But those laws originally imposed during colonial times remain largely in place elsewhere, even in a post-independence era.

In five countries around the world, same sex sexual conduct carries the death penalty while across the Commonwealth penalities for homosexuality include a 20-year jail sentence plus flogging. According to the HDT, half a dozen Commonwealth countries specify life imprisonment.

Last month the Prime Minister David Cameron used a Commonwealth summit to threaten the withdrawal of British aid from countries that fail to respect gay rights. Human rights barrister and director of HDT Jonathan Cooper refuses to be drawn on "aid conditionality" but says: "Our only purpose is the decriminalisation of homosexuality and the only way to do that is through the rule of law."

Cooper says that the organisation -- which has secured £2m of pro bono work from UK law firms over the next three years -- will aim to initiate at least five, and up to ten, cases a year.

The first case will be heard next month in Belize where the organisation will attempt to help overturn section 53 of the country's criminal code. This asserts that "every person who has carnal intercourse against the order of nature with any person or animal shall be liable to imprisonment for 10 years."

List of countries/regions criminalising homosexuality

Africa

1. Algeria

2. Angola

3. Botswana

4. Burundi

5. Cameroon

6. Comoros

7. Egypt

8. Eritrea

9. Ethiopia

10. Gambia

11. Ghana

12. Guinea

13. Kenya

14. Lesotho

15. Liberia

16. Libya

17. Malawi

18. Mauritania

19. Mauritius

20. Morocco

21. Mozambique

22. Namibia

23. Nigeria São Tomé and Principe

24. North Sudan

25. Senegal

26. Seychelles

27. Sierra Leone

28. Somalia

29. South Sudan

30. Swaziland

31. Tanzania

32. Togo

33. Tunisia

34. Uganda

35. Zambia

36. Zimbabwe

Asia

1. Afghanistan

2. Bangladesh

3. Bahrain

4. Bhutan

5. Brunei

6. some parts of Indonesia (South Sumatra and Aceh Province)

7. Iran

8. Iraq

9. The State of Jammu and Kashmir in India

10. Kuwait

11. Lebanon

12. Malaysia

13. Maldives

14. Myanmar

15. Oman

16. Pakistan

17. Qatar

18. Saudi Arabia

19. Singapore

20. Sri Lanka

21. Syria

22. Turkish Republic of Northern Cyprus (internationally unrecognised)

23. Turkmenistan

24. United Arab Emirates

25. Uzbekistan

26. Yemen

27. Occupied Palestinian Territory

Latin America & Caribbean

1. Antigua and Barbuda

2. Barbados

3. Belize

4. Dominica

5. Grenada

6. Guyana

7. Jamaica

8. St Kitts & Nevis

9. St Lucia

10. St Vincent & the Grenadines

11. Trinidad and Tobago

Oceania

1. Kiribati

2. Nauru

3. Palau

4. Papua New Guinea

5. Samoa

6. Solomon Islands

7. Tonga

8. Tuvalu

9. the New Zealand associate of Cook Islands