Britain is to end years of indecision by ratifying an international agreement aimed at preventing the loss of cultural and historic artefacts in conflict zones, amid growing outrage at the destruction by Isis militants of ancient sites in Iraq and Syria.

The culture secretary, John Whittingdale, is to introduce legislation that will finally sign the UK up to the 1954 Hague Convention, set up after the second world war to protect archaeological and historical sites, works of art, manuscripts, books and other objects.

About 115 countries have ratified the convention but over the years the UK government has cited a range of reasons for not following suit, including lack of parliamentary time and a belief that this is not an effective way to protect such treasures. One concern is believed to have been that ratification might leave the country open to renewed pressure to return the Elgin marbles to Greece, although there is nothing in the convention that would bind the UK to do so.

Whittingdale also announced that ministers would set up a “cultural protection fund” to help preserve cultural heritage in potential or existing conflict zones, and help with the recovery of artefacts. He is to convene a summit of senior government figures and cultural leaders from the British Museum, the V&A, the British Council and other key organisations – such as Unesco and the Red Cross – to advise on how to proceed.

In April one of the country’s foremost archaeologists, Lord Renfrew of Kaimsthorn, a Cambridge academic, said it was outrageous that the government was “dithering” over ratification at a time when Isis was threatening some of the world’s top cultural treasures.

The moves were welcomed by the director of the British Museum, Neil MacGregor, as “an important step towards safeguarding the world’s cultural property at risk in conflict zones”.

He added that the museum was developing, with colleagues in Iraq, a programme to establish a specialist corps of rescue archaeologists in the country.

“It is important to start this training now, as rescue archaeology will be essential as soon as it is once again possible to visit the key sites we believe have been damaged and to plan their recovery.”

While Isis has claimed responsibility for the destruction of artefacts in Mosul museum, and reports indicate that they were responsible for the bulldozing and looting of the historic sites of Nimrud and Hatra, the full extent of the destruction is not yet known, as archaeologists have not been granted access to the sites.

Last month, Islamic State group fighters advanced on the ancient ruins at Palmyra, raising fears that the Syrian world heritage site could face destruction of the kind already wreaked in Iraq.

Whittingdale said last night: “While the UK’s priority will continue to be the human cost of these horrific conflicts, the UK must also do what we can to prevent any further cultural destruction.The loss of a country’s heritage threatens its very identity. The knowledge and expertise of the experts in our cultural institutions makes us uniquely qualified to help. I believe that the UK therefore has a vital responsibility to support cultural protection overseas.”The Department for Culture Media and Sport said countries that were party to the convention were “required to respect cultural property situated within the territory of other parties by not attacking it, and to respect cultural property within their own territory by not using it for purposes which are likely to expose it to destruction or damage during armed conflict.”