The opposition party also termed the raising of cap on LPG cylinders from six to nine as a "farce".
"We criticise and condemn the decision because it will have a cascading effect on prices. This is an anti-people decision and that is why condemn it," BJP Spokesperson Prakash Javadekar told reporters here.
The party said the government's decision to increase diesel prices was a step "in disguise" and an attempt to hike the rates through the "backdoor".
It also demanded that the government must tell the real under-recoveries and bring necessary reforms in the oil sector before taking such a step and said the present under-recovery figures were "half-true and half-false".
BJP, however, did not make its stand clear on whether it was in favour of deregulation of diesel prices or not.
It said the time is not conducive for raising diesel rates as people in the country are already reeling under the pressure of spiralling prices.
"At this time, this hike is absolutely unjustified," he said.
On raising the cap on LPG cylinders from six to nine in a year, BJP demanded lifting of this rationing completely and said people should get as many as cylinders as they want.
"There is nothing to celebrate. This is nothing but an effort to raise the prices. BJP demands an end to rationing of gas cylinders," Javadekar said, adding that the public is being forced to pay up for the "inefficiencies" of the oil marketing companies.
The government today raised the cap on supply of subsidised cooking gas (LPG) to nine cylinders per household from six and virtually deregulated diesel prices allowing "small" hikes over a period of time.
The decision was taken by the Cabinet Committee on Political Affairs (CCPA) headed by Prime Minister Manmohan Singh and the new prices of diesel can come into effect from tonight itself.