More than a third of children under the age of four have televisions in their bedrooms, says a study.
The figure has risen dramatically from one in five two years ago. One in seven of the toddlers also has a video recorder.
The survey, by the Independent Television Commission, revealed that 52 per cent of under-16s have TV sets in their rooms.
The number of under-fours with a TV in their room increased from 21 per cent in 1999 to 36 per cent last year.
Children's welfare campaigners last night said the survey raised serious concerns about the viewing habits of youngsters.
Previous research has highlighted television's potentially harmful effects on children.
It has been blamed for causing sleep disorders, depression, anxiety and violent behaviour.
The study - Television: The Public's View - showed that the parents who spend more time in front of the TV are more likely to allow their children to have their own set.
Researchers also confirmed that there is a growing trend among parents to use videos and pre-school programmes to keep children occupied.
The Pre-school Learning Alliance warned parents to keep a close eye on the content of their children's viewing and the amount of time spent watching TV.
'Young children require many different types of stimulus to help them develop and learn and television can be one of these,' a spokesman said. 'But it must be used in moderation and preferably with parental interaction.'
The ITC survey showed many parents apparently do not stop their children watching unsuitable programmes.
Only 47 per cent said they prevent youngsters watching programmes they think are inappropriate. However, this was up from 39 per cent the previous year.
Those surveyed increasingly believe parents are responsible for what children watch.
Two in three see children's viewing as mainly the responsibility of parents, up 4 per cent on the previous year.
Violent content is most likely to cause viewers to turn off the television set.
The survey found 26 per cent of viewers had switched off due to violence, with 24 per cent doing so because of offensive language and 22 per cent because of sex and nudity.
A study last month warned that British children are becoming heavily addicted to television.
Researchers from the London School of Economics said youngsters in the UK watch around five hours of television a day, whereas the average in the rest of Europe is just two hours.
'The UK tends to stand apart as a country where screen entertainment, above all television viewing, is particularly important for children,' the report said.
Research published in January linked watching television and playing computer games with aggressiveness in children. Cutting down viewing time improved the behaviour of unruly children, according to the study by researchers at Stanford University in California.
Two years ago, a major study found that too much television could cause sleep disorders in youngsters, especially if they watch TV just before going to bed.
The American Academy of Paediatrics warned that allowing children to have televisions in their bedroom was a 'slippery slope'.
It went as far as recommending that children under two should not be allowed to watch television at all as it may harm their development.
The report said: 'The presence of a television in a child's bedroom may be a relatively under-recognised but important contributor to sleep problems in schoolchildren.'