Home Secretary Theresa May has admitted "international relations" were a factor in the Government's decision not to hold a public inquiry into the death of poisoned spy Alexander Litvinenko.
Mr Litvinenko, died aged 43 in 2006 after drinking tea poisoned with polonium at a London hotel.
Coroner Sir Robert Owen had requested that the government order the inquiry because he could not consider vital secret evidence as part of a normal inquest.
Today a letter from Mrs May to Sir Robert explaining the reasons for the decision was published.
It said: "It is true that international relations have been a factor in the government's decision-making.
"An inquest managed and run by an independent coroner is more readily explainable to some of our foreign partners, and the integrity of the process more readily grasped, than an inquiry, established by the government, which has the power to see potentially relevant to their interests, in secret.
"However this has not been a decisive factor and it if had stood alone would not have led the government to refuse an inquiry."
The Coroner's inquest into the death of former Russian spy Alexander Litvinenko can investigate the circumstances surrounding his death, the Foreign Office said today after the Government declined a request to hold a public inquiry.
A Foreign Office spokesman said:
We believe that the Coroner’s inquest can continue to investigate the circumstance of Mr. Litvinenko’s death and we will continue to co-operate fully with it.
The Government has declined a request to a public inquiry into the death of poisoned Russian spy Alexander Litvinenko. The Coroner only heard the decision this morning.
Coroner Sir Robert Owen says "an inquiry is necessary into Mr Litvinenko's death if is to be properly investigated".
Sir Robert Owen says he does not believe a proper investigation can be conducted and that it is of critical importance. He says he has not received a full and reasoned response from government and that it is regretted that the decision was not made until this morning.
The Foreign Secretary's lawyer apologises the decision has taken so long and Mr Hague will write to the Coroner with a full explanation about why this decision was reached.
The high court judge leading the inquest into the death of Alexander Litvinenko will today provide an update on calls to scrap it and replace it with a public inquiry.
Coroner Sir Robert Owen will hold a hearing at the Royal Courts of Justice after he previously ruled that vital secret evidence could not legally be considered as part of a normal inquest and asked the Government to hold an inquiry instead.
Assistant deputy coroner for Inner North London Sir Robert Owen has written to Justice Secretary Chris Grayling to request a public inquiry into the circumstances surrounding the death of poisoned spy Alexander Litvinenko.