International human rights groups have condemned the screening of Bhutanese refugees in Nepal to verify their nationality.
By Sushil Sharma
BBC correspondent in Kathmandu
They say the move would leave most of the 100,000 refugees stateless.
About 100,000 refugees from Bhutan live in camps in Nepal
In a joint statement, they described the verification process as a violation of human rights and urged international donors to reject it.
Refugee leaders say most of the migrants were forced to leave Bhutan as a result of ethnic cleansing.
A statement from six groups, including the London-based Amnesty International and the New York-based Human Rights Watch, follows an announcement by Bhutan and Nepal on Wednesday that a small number of Bhutanese refugees will be allowed to return to their country.
The rights groups said the move would not resolve the long-standing refugee problem.
A verification process of 12,000 refugees at one of the seven camps in eastern Nepal - undertaken jointly by both governments - identified less than 3% as bona-fide refugees who had the right to return to Bhutan.
More than 70% were dubbed voluntary migrants whose repatriation would depend on whether the Bhutanese government renewed their citizenship.
Bhutan had earlier refused to take them back, saying they had already forfeited citizenship by leaving the country voluntarily.
But refugee leaders claim that most of them had been forced to leave Bhutan in the wake of ethnic cleansing.
More than 100,000 refugees of ethnic Nepalese origin have been living in Nepal since 1990.
Nepal has insisted that all the refugees were Bhutanese nationals and that they had the right to return to their homeland.
Bhutan rejects the argument, saying it was ready to take back only genuine Bhutanese nationals, who numbered not more than a few thousand.
After several rounds of talks failed, Nepal and Bhutan agreed two years ago to carry out the verification of the refugees to determine their status.
Critics in Nepal said that the verification process and its results heavily favoured Bhutan and international groups appear to share that view.
Ingrid Massage, a spokesperson for the London-based Amnesty International said the decision taken on Wednesday's decision could send out the wrong signals.
She said it may encourage other governments to arbitrarily deprive whole ethnic groups of their nationality, expel them from their country, and then refuse to accept them back.
Ms Massage cautioned Bhutan's donors against endorsing a process that she said could render tens of thousands stateless.