More than 3,000 export licences for the sale of arms and other military-related equipment to states on the Foreign Office's list of countries of human rights concern have been issued and remain in force, MPs have found.
The Commons Committees on Arms Export Controls (CAEC) said the combined value of the individual export licences alone came to more than £12 billion.
Among the countries for which licences for strategically controlled goods have been issued are Iran, Sri Lanka, Saudi Arabia, Russia, China and Belarus. Three licences still remain valid for Syria.
Of the 27 nations on the Foreign Office list of countries of human rights concern, there are no valid licences for just two - North Korea and South Sudan.
While the CAEC acknowledged many of the licences were for dual-use (military or civilian) items or other equipment which could not readily be used for internal repression, it said the numbers were still "surprisingly large"
The countries for which the largest numbers of licences have been issued include China with 1,163 with individual licences worth £1.4 billion, Saudi Arabia with 417 licences and a value of £1.8 billion, and Israel and the Occupied Palestinian Territories with 381 licences and a value of £7.8 billion.
CAEC chairman Sir John Stanley said: "The scale of the extant strategic licences to the Foreign Office's 27 countries of human rights concern puts into stark relief the inherent conflict between the Government's arms exports and human rights policies.
"The committees adhere to their previous recommendation that the Government should apply significantly more cautious judgments when considering arms export licence applications for goods to authoritarian regimes 'which might be used to facilitate internal repression' in contravention of the Government's stated policy"
The CAEC also strongly condemned the Government's "reprehensible" failure to lobby other countries to follow its lead in imposing tighter controls on exports to Argentina, despite recent claims by Argentine foreign minister Hector Timerman that it would not take "another 20 years" for them to regain control of the Falklands.
The Foreign Office's list of countries of concern comprises Afghanistan, Belarus, Burma, China, Colombia, Cuba, North Korea, the Democratic Republic of Congo, Eritrea, Fiji, Iran, Iraq, Israel and the Occupied Palestinian Territories, Libya, Pakistan, Russia, Saudi Arabia, Somalia, South Sudan, Sri Lanka, Sudan, Syria, Turkmenistan, Uzbekistan, Vietnam, Yemen and Zimbabwe.
Argentina is one of five additional countries about which the CAEC has raised concern - the others are Bahrain, Egypt, Madagascar and Tunisia.
The CAEC is made up of the the Commons Defence, Foreign Affairs, International Development and Business, Innovation and Skills committees.
Labour MP Richard Burden, who chairs the Britain-Palestine All Party Parliamentary Group, said: "Many of the countries on the list are in the Middle East and North Africa.
"But what is most striking is that over half of the total is going to 'Israel and the Occupied Palestinian Territories'.
"Look a little closer and you see that almost all of those exports are going to Israel, with only £5,539 going to the Occupied Territories.
"Look closer still and you see something utterly astonishing - 380 different licences have been granted for exports of arms and military equipment to Israel. However, £7,765,450,000 of the £7.8 billion worth of equipment exported to Israel is covered by just one licence approval - for equipment employing cryptography and software for equipment employing cryptography.
"This is bizarre, particularly as there are scores of other licences granted for export of cryptography equipment and software which have a substantial value - but still only add up to a tiny fraction of this amount.
"I am tabling questions to the minister today to find out just what this licence was all about. Is just one company involved? Why does the scale of this licence dwarf all others with similar titles? What does the contact actually involve?"
A Department for Business, Innovation and Skills spokesman said: "The Government takes its export responsibilities very seriously and operates one of the most rigorous arms export control regimes in the world. An export licence would not be granted where we assess there is a clear risk the goods might be used for internal repression, provoke or prolong conflict within a country, be used aggressively against another country or risk our national security.
"All licences highlighted in the Committees' report were fully assessed against a range of internationally agreed stringent criteria which take into account the circumstances at the time the licence application was made.
"When circumstances change or new information comes to light we can - and do - revoke extant licences where the proposed export is no longer consistent with the criteria."
Amnesty International's arms control expert Oliver Sprague said: "Looking at these, the Government's own figures, it would be hard not to conclude that the UK government's arms sales practices are at odds with its stated policy not to send weapons to anywhere that poses a clear risk that they could be used for human rights violations.
"What is needed now is an urgent explanation of what these licences were actually for, who was going to use them and what assurances were in place to ensure they were not going to be used for human rights violations. Until there is much greater transparency over exactly what we are selling and to whom, it will be impossible for Parliament or the public to have confidence in the UK's arms sales policies."