Critics say a bill currently before Pakistan's Parliament to increase fines for eating and drinking in public during Ramadan, alongside jail terms of up to three months, is evidence of increasing intolerance in the country.

With temperatures on the eve of Ramadan in much of Pakistan 40 degrees or above, opponents of the hiked penalties for public eating or drinking in daylight hours have warned the vulnerable will suffer.

"People are going to die from heatstroke and dehydration, this is a ridiculous law..." tweeted Bakhtawar Bhutto-Zardari, the daughter of former Pakistani Prime Minister Benazir Bhutto, adding "this is not Islam".

Citing a need to more effectively preserve the sanctity of Ramadan, the religious affairs committee of Pakistan's Senate unanimously approved ten-fold increases in the maximum fines for fast-breakers, alongside prison terms of up to three months.

The committee's chairman, Maulana Hafiz Hamdullah, told the ABC some cinemas had even been screening movies, which he said was unacceptable.

"Any kind of violation of Ramadan, be it in hotels, cinemas or any other public place, this will have negative impact," he said.

The fines are not massive — $A10 to $A300 for individuals, up to about $A650 for businesses.

But that was not the point, opponents argued.

Tahira Abdullah, a noted Pakistani rights activist, said the plan went against "the spirit of Islam as I know it".

She believed the targets were religious minorities.

"When you close down all restaurants and hotels and access to food and water and drinks during the month of Ramadan, what about non-Muslims?" she asked.

"How can a state force them to fast?"

But Senate Committee chairman Maulana Hamdullah denied the law was aimed at non-Muslims, saying instead that it reflected Pakistan's establishment as an Islamic republic.

"Pakistan is an Islamic republic. Article 2 of the constitution states that Islam shall be the state religion of the country," he said.

Mr Hamdullah said it would not stop people from eating, provided they did so in private.

"As followers of country's constitution, they [non-Muslims] should avoid eating in public places. They should eat at their homes," he saod/

Concerns legislation could encourage vigilantes

But rights campaigner Tahira Abdullah worried that if passed, the legislation could have a more insidious effect, emboldening vigilantes.

She pointed to Pakistan's contentious blasphemy law, frequently invoked by religious mobs intent on dispensing rough justice.

"The blasphemy laws have been misused for property vendettas, personal vendettas," she said.

"Laws which are open to misuse and abuse and exploitation, need a long hard look by Parliament, including the new ordinance pertaining to fasting in Ramadan."

Mr Hamdullah said the bill would be debated next month.