Professor Blum said the effect of having a single-parent was minor and that the important factor was that children had at least one adult they felt connected to.

"It doesn't matter if parents work," says Professor Blum

He gave his findings to a parenting conference in London organised by the National Family and Parenting Institute.

He says parents should aim to see their children at four key times of the day - early mornings, immediately after school, dinner time and bed time.

Professor Blum, of the University of Minnesota, says rather than organising lots of joint family events, parents should supervise their children's free time, or get another adult they trust to do so.

This supervision he says is crucial, particularly in preventing children from developing problems with drink and drugs.

Time to talk

"It is not about going to the football match or going to the shopping mall with them," he said.

"Be available when they need to talk, don't hesitate to talk to them even when you think they're not listening and when you are talking, turn off the television."

Professor Blum says if he had to choose one key point in the day where parents should talk to children it would be dinner time.

He says the question of whether parents work is not important - it is the relationship they have with their child which is the key factor.

Daphne O'Keeffe: "Children respect honesty"

Parents who are working could try to make up for not being there at certain times of the day by leaving notes or telephoning, he says.

Daphne O'Keeffe says she does not spend as much time as she would like with her son James because she works long hours.

But she does not think this has damaged their relationship.

"Children are very respectful of truth and honesty and if you can honestly say 'this is the time I have to spend with you', it isn't a problem," she said.

Her son James agrees: "I think it works because we see enough of each other and have a good time but we still both like to have our freedom."

The American study was of children aged between 12 and 18.

The children were asked questions about how close they felt to their parents and about their relationships with friends and teachers.

They have been followed for six years and asked about their use of drink and drugs, about depression, sex and teenage pregnancy.