Human Rights Day is the anniversary of the signing of the Universal Declaration of Human Rights (UDHR) on 10 December 1948, one of the most important documents in human history. Drafted by representatives from many countries and cultures, and endorsed today by all 192 member states of the United Nations, it embodies a global humanitarian consensus.

Rejecting the doctrines of cultural and moral relativism, which have long been promoted by imperialists and, more lately, by some advocates of anti-imperialism, the UDHR asserts that all peoples in all cultures are entitled to the same rights and freedoms.

The big problem is adherence and enforcement. The UDHR is a noble document but even western democracies like the UK and US fall short of its ideals. Britain has house arrest without charge, libel laws that inhibit free speech and restrictions on the right to peaceful protest near parliament. Many US states still have the death penalty and people merely suspected of terrorism have been kidnapped, tortured and detained without trial at the behest of the US government.

Other grave human rights abuses – such as religious persecution, ethnic cleansing, media censorship, rigged elections and trade union suppression – are widespread in many countries, including Saudi Arabia, Belarus, Uganda, Zimbabwe, China, Iran, Burma, Sudan, Russia, Pakistan and Iraq, to name just a few. There is, however, no objective, transparent measure to determine a country's conformity to, or departure from, human rights norms.

These deficiencies need to be addressed if the international community is to secure human rights progress. We need benchmarks against which all countries can be measured, without fear or favour. There is no easy way to ensure that the principles of the UDHR are upheld by UN member states but the power of publicity and moral leverage should not be underestimated. Even tyrannies are conscious of their image and seek to avoid opprobrium.

This is why the Green party of England and Wales is advocating a UN Global Human Rights Index, as a means of measuring and ranking human rights abuses, country by country. The aim is to create a human rights league table to pressure governments to clean up their record. "Our proposal makes the case for the UN to publish an annual Global Human Rights Index, detailing the human rights performance of each and every government on the planet, displayed in a league table form," said Dr Richard Lawson, Green party member and founder of the campaign for the Global Human Rights Index. Speaking at the launch of the index idea last year, he said: "This will enable the relative human rights standing and trends of each country to be seen at a glance. It would add pressure on the worst ranked countries to improve their human rights record."

Since the index idea was first mooted, interest has been expressed by campaigners with World Concern, Global Action Plan to Prevent War, World Disarmament Campaign, Arms Reduction Coalition, Culture Change and the Movement for the Abolition of War. We are planning to approach the United Nations Association, the Foreign Office and the European Union.

The current draft of the index was finalised in 2008. Over many months, I worked with Lawson to map out the rights and freedoms to be covered by the index, and how the ranking system would be calculated. What we have devised is a draft outline, open for discussion, negotiation and further refinement.

Using a points system, the index measures every country, based on its compliance with a checklist of 52 human rights norms, such as whether or not it has the death penalty, torture, detention without trial, freedom of the media, the right to protest and equal rights for women and for ethnic and sexual minorities. This would enable objective comparisons between the human rights records of different countries and whether each country's record is improving or deteriorating.

The human rights trend of nations over time would therefore be demonstrable and transparent. This would give an important early warning signal about which states are increasing their human rights violations. These countries could then be pressed by the UN to remedy the abuses and, if necessary, given assistance to do so – perhaps in the form of UN peacekeepers, in instances of ethnic or religious violence.

At present, repressive states are dealt with in an arbitrary and ad hoc way by politicians, often through media manipulation. Iran's regime is deservedly condemned, while there is barely a squeak of protest about the equally gross human rights violations by a western ally like Saudi Arabia.

The UN's failure to tackle human rights-abusing nations will be harder to justify or ignore if the index clearly ranks them as major abusers. Conversely, the unfair or excessive demonisation of a particular country will be less easy to accomplish if the index can show that it is not the worst offending state or if the index can demonstrate that the accusing states also have a less than exemplary human rights record.

The index could be cited as evidence to justify UN legal action and targeted UN sanctions against the very worst offenders. This might act as a wake-up call to regimes near the bottom of the index. Knowing that they could be next in line for prosecution and sanctions, their leaders might decide to take pre-emptive action to improve their observance of human rights.

The index will not prompt every country to reduce its human rights violations. Certain tyrannies are likely to carry on regardless. But the index might encourage some nations to make improvements. However small, any betterment of human rights is a gain for people whose rights have been previously abrogated.

Britain and the EU have the power and influence to take the index proposal to the UN and get it discussed. Over to you, David Miliband and Catherine Ashton.