There is no prospect of Burma's first elections in two decades being "free, fair or inclusive", Downing Street said today.
Prime Minister Gordon Brown said that the military regime which has ruled the south-east Asian state for almost half a century had "squandered" the opportunity for national reconciliation offered by the upcoming poll.
He called for pro-democracy campaigner Aung San Suu Kyi - who has been banned from standing in the election - to be allowed to take her place in the Burmese political system.
The Nobel laureate's National League for Democracy, which won the last elections in 1990 but was blocked from taking power, has announced that it will boycott this year's vote, for which a date has yet to be set.
The decision was taken after this month's enactment of new election laws which bar Dr Suu Kyi and other convicted political prisoners from standing in the poll.
The NLD's pullout has raised further questions over the credibility of the military-organised election, part of a "roadmap for democracy" offered by the Burmese junta which critics say will only strengthen their grip on power.
Suu Kyi, who has been under house arrest for 14 of the 20 years since she was elected Prime Minister, recommended a boycott, denouncing the laws governing the poll as undemocratic.
Mr Brown today said: "Sadly, the Burmese regime has squandered the opportunity for national reconciliation.
"Aung San Suu Kyi must be allowed to take her rightful place at the heart of Burmese politics."
Mr Brown's spokesman added: "Regrettably, recent announcements mean there is no prospect of (the elections) being free, fair or inclusive."
The NLD's boycott has sparked speculation that Burmese voters may express their frustration at the repressive government of their country by staying away from the the polls.
But it also means that the League will fall foul of new laws which state that parties failing to register for the vote must be dissolved.