Congress today expressed serious concern over the sharp increase in prices of petrol. Briefing media in New Delhi Party Spokesperson Manish Tiwari said that the increase of five rupees a litre in just one month is unfair on the consumers. He said that the rationale behind the hike should be made public by the Oil Companies. He hoped that the government will intervene if the reasons for the increase are not justified. Manish Tiwari however said that the diesel prices which have not been de-regularized have a cascading effect on inflation.