The flexi fare pricing of railway tickets in three premium trains is on an "experimental basis", senior officials of the Railway Ministry said on Thursday, as political parties criticised the hike and demanded its roll back.

"Flexi fare pricing is on experimental basis," a senior official of the Ministry told IANS requesting anonymity.

"We will check what is the impact of the flexi fare pricing in the Rajdhani, Shatabdi and Duranto express and then a decision would be taken after study of the impact on passengers," the official added.

The officer said that the three trains together ferry only about 0.6 per cent of the total 2.3 crore passengers that the Railways carries every day.

"We run about 12,000 passenger trains everyday, but this flexi fare pricing is implemented only on 152 trains," the officer added.

The officer also said the flexi pricing move was based on the travel experience of passengers on select trains that are highly patronised. "We couldn't have experimented it on any other trains as it would have affected a number of people," the official added.

"We could not have implemented it on the executive class too as the fares would have become comparable to air fares," the officer said.

The officer said that the surge pricing would also help stabilise the tatkal quota ticket prices, which earlier would be higher under the premium tatkal quota.

The Railways on Wednesday announced implementation of the flexi fare pricing on the Rajdhani, Shatabdi and Duranto express trains from September 9.

According to the new fare system, the base fares of these trains will increase by 10 per cent with every 10 per cent of berths sold, subject to a prescribed ceiling limit.