The contested life of one of Britain's best-loved poets, Ted Hughes, has found controversy once more after his estate stopped cooperating with his latest biographer, Jonathan Bate.

Shakespeare scholar Bate began working on a biography of Hughes in 2010 though has been barred from private archives and asked to return photocopies of privately held documents by the poet's estate. He is no longer has the right to quote extensively from the poet's work.

According to Bate, the decision to withdraw support came "completely out of the blue," though the estate was apparently becoming "impatient" to see more of the book.

"The estate was insistent I should write a 'literary life', not a 'biography'," he said, ".and wanted to see more sample chapters, in order to ensure I was only writing about life-events that impinged upon the literary life."

However, just days before Bate was due to send 100,000 words, the estate informed him that he was no longer able to quote from the Hughes archive. The archive was bought by the British Library from his widow, Carol Hughes, for £500,000 in 2008.

"I have discovered some things that surprised even Carol and Olwyn, Ted's sister, so there may be more surprises to come," said Bate. His research had so far uncovered numerous unpublished poems as well as evidence that Hughes began working on Birthday Letters almost from the day Sylvia Plath died.

Ted Hughes turbulent first marriage to Plath began in 1956. She took her own life in 1963 and Hughes married Carol Orchard in 1970. The poet had been condemned for burning Plath's last journal, saying he did not want her children to have to read it. He is believed to have lost another journal, as well as an unfinished novel.