The new Environment Secretary has given water company chiefs two weeks to set out “significant improvements” to prevent sewage being dumped in open water.

Ranil Jayawardena also faced calls from Labour for “tougher sanctions”, including prison sentences, for water bosses responsible for pumping effluent into the UK’s rivers and beaches.

He told the Commons: “The volume of sewage spewed out by water companies is completely unacceptable and the public have rightly shown their outrage.

“Yesterday, in my first day in office, I told water chief executives that it is not good enough and I have instructed them to write to me formally by September 21 with a plan on how they are going to make significant improvements.

“I met the Environment Agency and Ofwat too, and told them that they should use every enforcement power available to them to make sure there is compliance, and I will not hesitate to take further action if I do not see the pace of change that this House expects.”

Over the summer, the Liberal Democrats campaigned on preventing sewage pollution, leading to Mr Jayawardena accusing them of having done “nothing” to prevent the problem while they shared power with the Conservatives in the 2010-2015 coalition government.

Lib Dem MP Sarah Olney demanded that “Southern Water compensates Sussex seaside businesses” after sewage spills led tourists to avoid the county’s beaches.

Mr Jayawardena replied: “First of all, I have set out already to the House what I intend to do. Second, I would observe that the Liberal Democrats’ plan is to simply play politics with this serious issue.

“When they were in Government, they did not take the action that we have done now and what they are calling for, sadly, and this is a serious point, what they are calling for out there in their leaflets is calling for sewage to flow back into people’s homes, because that is the consequence of doing what they are proposing.”

Shadow environment secretary Jim McMahon later called for stronger sanctions to punish water bosses who do not prevent sewage dumping.

He told the Commons that “over the summer, the Government allowed water bosses to dump sewage on 90 beaches”, adding: “Without tougher penalties in place to make sure that it hits the bottom line, they will not change their behaviour, and it’s got to include tougher sanctions including prison sentences. Does he agree?”

The Environment Secretary said: “He clearly was not listening when I set out my plan a moment ago. First of all, they are reporting back in two weeks.

“Second, we have legislated on this side of the House to issue unlimited fines through a criminal process, and we will not hesitate to do more.”