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 It took until the 1967 Sexual Offences Act before England and Wales repealed its own legislation and until the 1980s before Scotland and Northern Ireland did the same.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