The director of this year's International Yeats Summer School has criticised two former directors of the school for their interpretation of the poem Easter 1916, accusing one of using "loaded and partisan language" in relation to the Rising itself, and the other of being "firmly on the wrong track".

While expressing concern that his remarks might seem ungracious to friends of the summer school "who I also like to think as friends of mine", Prof Patrick Crotty from the University of Aberdeen told students in Sligo that poetry was "too important to be spoken about in a dissembling manner".

In his lecture Easter 1916 and the Critics, Prof Crotty reserved his strongest criticism for Declan Kiberd, saying while he had produced books on Irish literature marked by copiousness, good cheer and delight in ideas, his prose was sometimes "provocative where it might be suggestive" and "reckless where it might be judicious".

Quoting from Kiberd's analysis of Easter 1916 in his book Inventing Ireland, Prof Crotty said the language was loaded and partisan in its description of the rebels as "heroes" and some of Ireland's "most gifted thinkers". He accused Kiberd of misrepresenting the poem when he said what appalled Yeats was the loss of gifted thinkers.

"There is a rather nasty subtext in Kiberd's remarks, a worryingly genuine sectarian implication to put beside the spuriously imperialistic one he detects in the poem," Prof Crotty maintained.

He told his students Kiberd had identified Yeats with the colony and characterised him as an unconscious imperialist, which "sounds like another way of saying that Yeats is a Protestant and can therefore never fully belong to the national formation which embraces such gifted thinkers as Pearse and McDonagh".

While expressing concern that he was disagreeing with former directors, he also took issue with Harvard's Prof Helen Vendler's suggestion that the poem was an elegy.

Calling her argument "unconvincing", he said she was "on the wrong track", insisting the poem was less concerned with death than with birth as the closing words - "a terrible beauty is born" - make clear.

Prof Crotty pointed out that the poem is widely regarded as the 20th century's most famous political poem in English. He said its impact on events in Ireland since its publication in 1920 had been exaggerated, but "few would question its reality".

He said he would not get into the "unresolvable argument" about whether the poem sent out certain men to be shot by the English or the Irish. His concern was with the literary and critical responses to the poem, many of which he believed involved misreading of the text itself or its political context.

The school continues today with a lecture by Dr Bruce Stewart from the University of Ulster on Yeats and Joyce, while Dr Nicholas Allen from the University of North Carolina will speak on Civil Wars: WB Yeats, Jack Yeats and 1922.