The British Union for the Abolition of Vivisection has written to Ed Miliband, Minister for the Cabinet Office, to complain about a Home Office consultation on the publication of statistics on animal testing.
Buav said it had received a letter in early December that gave it only 14 working days to respond. The Compact says consultations should last a minimum of 12 weeks.
The Home Office, named by the NCVO's Compact Advocacy Programme in March 2007 as the worst offender for Compact breaches, said the exercise was not a formal consultation.
"We are determined to deliver on our better regulation promises to reduce unnecessary red tape," a spokesman added.
Michelle Thew, chief executive of Buav, said the Home Office was being "underhand". She said: "Slipping out a curtailed consultation just before Christmas was meant to deny the public an opportunity to debate."
Ingela Andersson, Compact advocate for the NCVO Compact Advocacy Programme, said: "There is no excuse for the Government running such short consultations. It begs the question whether it was genuinely looking for people's views."