The Organization for Security and Cooperation in Europe said parliamentary elections last weekend in Belarus were "not competitive" nor were general political freedoms respected.
A spokesman for the British Foreign and Commonwealth said, while London welcomed some reforms embraced by the government in Minsk, the assessment by the OSCE was a disappointment.
"We call on the government of Belarus to work constructively with the OSCE on further reforms," the statement read.
OSCE observers said more candidates were able to compete in the election, though many influential opposition leaders remained behind bars.
Stefan Fule, commissioner for enlargement and European neighborhood policy, delivered a message of support to rights activist Ales Bialiatski, considered a political prisoner in Belarus.
"There is nothing to justify the treatment you are facing," Fule said in a statement. "On every occasion we repeat our demand to the Belarusian authorities to immediately and unconditionally release and rehabilitate you."
Bialiatski was sentenced to more than four years in prison in November for what Fule said was his support for human rights.