The statistics body says all the questions are justified
The independent statistics watchdog has criticised the Conservatives for claiming the next census will "snoop" into peoples' private lives.
The Tories said questions set to be asked in the 2011 survey on numbers of bedrooms and overnight visitors showed ministers had no "respect for privacy".
But the Statistics Authority said the claims were "ill-founded" and the government had no say in the questions.
The Tories have yet to comment on a letter sent to them by the watchdog.
It is the first time the watchdog has taken issue with the opposition over an issue relating to statistics since it became independent of government.
Everyone in the UK has to answer the questions in the census - which is held every ten years - or potentially face fines.
For the first time in 2011, people will be asked to provide details of the number of bedrooms they have as well as the names, sex and birth dates of any overnight guests in their homes.
Conservative spokesman Nick Hurd said such questions were "intrusive" and accused ministers of acting like "bedroom snoopers".
He also suggested the questions would make the census less accurate as people might be inclined not to tell the truth.
But the Statistics Authority said suggestions the questions were a "licence" to snoop into peoples' lives were "ill-founded."
In a letter to Mr Hurd, the watchdog's chairman Sir Michael Scholar said the questions were decided by its officials after extensive consultation.
"It is quite wrong to give the impression that they are initiatives of government ministers," he wrote.
The information about bedrooms would help councils know whether properties were overcrowded, he said, while questions on overnight visitors would give a more accurate picture of the population by identifying people away from home.
"We need the census to know as best we can the size and distribution of the population, to provide a basis for the allocation of very large sums of public money to local government, the NHS and elsewhere," he added.
Ministers have previously said all the questions in the census would be justified in the public interest.
The census, designed to give a snapshot of demographic and social changes in the UK, must be approved by Parliament in advance.
The Statistics Authority has shown it is prepared to intervene when it believes statistics are being misused for party political ends.
In the most high-profile row since its independence, it criticised ministers in December for putting pressure on officials to release what it said were "selective" figures on knife crime.