Environment Secretary Owen Paterson has urged water companies to "look closely" at whether price increases are necessary and introduce special tariffs for hard-pressed households.
In a letter to suppliers, Mr Paterson said they should recognise the financial strain that people were under.
The intervention came with Ofwat expected later this week to reject an application from Thames Water to increase bills by £29 in 2014-15.
The regulator has questioned the profits being made by firms, and suggested its next Price Review could ease the upward pressure on bills by up to £750 million after 2015.
Mr Paterson said: "We know that household budgets are under pressure, and keeping water bills affordable is a crucial way we can help hardworking people.
"That is why we are pressing hard to make sure customers get a fair deal, by encouraging water companies to look closely at any price increases, introduce social tariffs for vulnerable customers and crack down on bad debt."