"The central governmment's decision will have dangerous consequences. It will heighten inflation," All India Trade Union Congress (AITUC) general secretary Gurudas Dasgupta said here.
Terming the step as the "biggest anti-people decision" of the UPA government, he said: "In a few days, diesel prices will be up by Rs.5 to Rs.6. There will also be a spiralling effect on food inflation".
Tapan Sen, general secretary of the Communist Party of India-Marxist-affiliated Centre of Indian Trade Union (CITU), said the decision will add fresh fuel to the fire of inflation.
Public transport and goods transport will be dearer "and the centre is actually trying to do away with the public transport system".
In a reformist move, the central government Thursday allowed state-run transport fuel retailers to revise diesel prices marginally and periodically without prior government consent.