The Turkish parliament was yesterday preparing to ask the UK to repudiate a historical document that is considered to form the basis of the claim that Armenians were victims of genocide by Ottoman Turks during the first world war.

The initiative comes on the eve of Sunday's 90th anniversary commemorations among Armenians of what they regard as the start of the massacre of up to 1.5m people.

The move is likely to exacerbate the bitter dispute between Turks and Armenians. Supporters of the Armenian cause, particularly in France, are lobbying for the European Union to delay the start of Turkey's accession talks for EU membership until Turkey acknowledges a 'systematic extermination' in 1915.

Turkish MPs completed and signed a letter to both houses of the UK parliament arguing that the document was 'a fraud based on fabrications, half truths and biased reports and perceptions' of what happened and 'a masterpiece of propaganda and tool of deception'.

The Financial Times

The document, The Treatment of Armenians in the Ottoman Empire 1915-1916, was written by the British historian Arnold Toynbee and included in a publication known as the Blue Book, by Viscount Bryce, a British diplomat. It was an official Westminster document, which is why the Turkish parliament wants the House of Commons and House of Lords to act.

Turkey rejects the charge of genocide. It insists that the true death toll among Armenians was about 600,000 and that many died from the effects of civil war, starvation and deportation. It says the deaths of hundreds of thousands of Turks at the time are overlooked.

The letter, which was made available yesterday by the Turkish parliament in the original Turkish and in English translation, will be sent to London imminently.

The letter says British propaganda in the first world war aimed to portray the destruction of the Ottoman Empire as a key aim of the war, to 'render British colonialism in Anatolia and Mesopotamia palatable', and to encourage the US to join the Allied side. The Ottoman Empire collapsed into many nations after the war. Its Anatolian heartland is now Turkey.

The British embassy in Ankara declined to comment on the letter. Some Turkish historians say the document has stood the test of time; others say Mr Toynbee later distanced himself from its findings, which were based on eyewitness accounts.

The official UK position is that the massacres were 'an appalling tragedy' but that the evidence is not 'sufficiently unequivocal' to categorise them as genocide under the 1948 United Nations Convention on Genocide.

The letter is the initiative of Turkey's main opposition People's Republican party, which has shaped Ankara's longstanding opposition to any official acceptance of the genocide claim. Diplomats said it appeared to be an attempt to prevent the ruling Justice and Development party from diverging from that policy.