Tory MP Richard Benyon said there is "no way" a 15ft hose was left running at the family estate in his constituency of Newbury in Berkshire.
The claims were made in The People. The newspaper says it stands by the story.
But the MP reported the paper to the police and has written to the Press Complaints Commission (PCC).
The People claimed a reporter spotted the hose running when he called at Mr Benyon's house to speak to him about the hosepipe ban.
It said a 15ft hosepipe was found "gushing in the grounds" of the Tory MP's family estate, called Englefield House.The People said it had "called to see him" the day after the hosepipe ban "came into force for more than 20 million taxpayers".
But Mr Benyon, a minister at the Department for the Environment, Food and Rural Affairs (Defra) who has previously defended the hosepipe ban, said: "Neither I, nor my family, nor anyone who works for me turned that hose on.
"I leave it for others to make a judgement as to who, therefore, did."
He added: "A reporter was seen walking up the steps."
The newspaper denies it turned on the tap.
It said in a statement that it stood by the story and was satisfied it was true.
It said a reporter knocked on Mr Benyon's door to speak to him about the hosepipe ban, but the call was not answered. The reporter saw a hosepipe running in the grounds and so called a photographer, it said.
The statement added: "We then called the house to alert them and the man who answered thanked us and said he would tell the head garden manager.
"Approximately 34 minutes later Mrs Benyon arrived to turn off the tap and said: 'I have no idea why the hosepipe's on and I will go and turn it off.'
"When asked who was responsible for leaving it running, she said: 'I have no idea. I'm not passing the blame.'"
Complaint letter
A spokesperson for Defra said: "Mr Benyon has reported to Thames Valley Police an incident of trespass on his property on the afternoon of the 6 April and the actions thereafter."
A letter of complaint has also been sent to the transitional body of the PCC, set up in the wake of the Leveson inquiry and the phone hacking scandal.
A police spokesperson said: "Thames Valley Police were notified about an incident at a property in Englefield, West Berkshire on Friday 6 April.
"However, the caller did not require police attendance and there is no further police involvement."
Hosepipe bans affecting about 20 million customers were introduced by seven water authorities in parts of southern and eastern England on Thursday.
People who flout the bans, which follow one of the driest two-year periods on record, face fines of up to £1,000. (Source: bbc.co.uk)
