The new sugar tax is unlikely to persuade poor, overweight people to eat less, but is likely to make them poorer, according to Scottish researchers.

It argues that the way to tackle the UK's weight problem, is to tackle the causes of inequality.

In last week's budget, the Chancellor George Osborne announced a tax on the makers of sugary soft drinks, in order to tackle childhood obesity.

AG Barr, makers of Irn Bru, said they had already cut sugar levels so the measure was "extremely disappointing".

Now an academic study claims to provide the first experimental evidence of the connection between poverty and obesity, showing that people who see themselves as being poor are more likely to consume more. Its director says food campaigners such as Jamie Oliver should understand that connection in case they do more harm than good.

The study led by St Andrews University has discovered the psychological links between poverty, inequality, and food consumption.

The research, published by the international research journal Appetite, was undertaken by Dr Boyka Bratanova, a lecturer in Management at the St Andrews University. It also suggests that people eat more calories to ‘self-soothe’ a sense of anxiety when they feel unequal to others.

Dr Bratanova said "The introduction of consumption tax, like the recently introduced sugar tax by the Chancellor George Osborne, is essentially a flat rate tax, and it hits the poorest the hardest. Provided they consume high calorie food to satisfy a psychological instinct, punishing them with higher tax seems unfair.

“People who feel poor would probably continue to eat high calorie food at a similar rate as this food provides them with a higher caloric yield. This is hard to overturn, because the urge comes from a perception of their economic reality. So getting them to pay a higher price is unlikely to drastically change their consumption behaviour, but it is likely to push them further into poverty.

Dr Bratanova worked with a team of international researchers, from the Université Libre de Bruxelles, the University of Edinburgh and the University of Melbourne. She said, “Feeling poor and feeling unequal can simultaneously influence eating behaviour, pushing people to approach high calorie food and consume larger amounts of it."

Her team tested the hypotheses that perceived poverty triggers increased food consumption, by conducting studies of two groups. One saw themselves as poor, and were manipulated to do so, and the other that they were wealthy.

The 'poor' participants ate on average 54% more food than participants induced to feel wealthy.

Additionally worries that others would look down on them, or alternatively that they were envied, were also associated with increased calorie intake.

Dr Bratanova said she hoped that the findings would be used to re-evaluate tax and education-based interventions aimed at obesity treatment and prevention.

She said “Campaigns based around education are also likely to induce guilt in poor people, because they convey the message that choosing what to eat is within an individual's control. Instincts, however, are difficult to control.

“Taken together, the poor in a society seem to have it the worst – they carry the burden of poverty, suffer emotionally from relative deprivation, pay higher proportion of their incomes in consumption tax, and feel guilty and inadequate because of their eating behaviour. I am sure public health campaigners, including Jamie Oliver, have their heart in the right place; however, understanding the psychology that links poverty, inequality, and eating behaviour is important so that we don’t do greater harm than good. Addressing the root causes, poverty and inequality, would be the ultimate solution of the obesity crisis.”