Brighton and Hove's controversial schools places lottery has failed to reduce segregation between rich and poor pupils, research suggests today.

Richer pupils are still dominating places at top-performing schools in the city, and poorer pupils are missing out because of the way school catchment areas are drawn up, according to a study by the Institute of Education and Bristol University.

Brighton and Hove introduced a lottery system, the first of its kind, two years ago following concerns that there were unequal opportunities throughout the country for rich and poor families to access the best schools.

The theory behind the council's reforms was that by using a lottery instead of the distance from a child's home to a school as a measure of allocating places, every child would have the same chance of winning a place.

Alongside the introduction of the lottery, new catchment areas were drawn up. Within each of these catchment areas allocations for places is random.

Today's study, which looks at the first two years of the lottery, concludes that there have been "winners and losers", but so-called "social segregation" - the dividing of pupils based on family income - has not significantly reduced.

It says that the way the new catchment areas have been established means that in general, families in the poorest neighbourhoods still have little chance of getting into the popular schools that are in the city centre.

This is because a particular school may not be in their catchment area.

The study says: "There are clearly winners and losers from these reforms: some students are attending less academically successful secondary schools than they might have expected to; for others the reverse is true.

"The location of these winners and losers largely derive from the design of the catchment areas rather than the impact of the lottery where it applies."

The report authors, Rebecca Allen of the Institute of Education, and Simon Burgess and Leigh McKenna of the Centre for Market and Public Organisation at Bristol University said: "The main lesson of our analysis is that the introduction of a lottery on its own is not enough to equalise access to the high-performing popular schools.

"The drawing of the catchment area boundaries is central to the outcome of the reform."

The study says it will be "several years" before the impact of Brighton and Hove's reforms will become clear because families are expected to move, and house prices will adjust in response to the new catchment areas.

It adds: "It seems unlikely that the reforms are likely to substantially lower social segregation across schools even in the long-run in this city where differences in the quality of housing stock across areas are deeply entrenched and the boundaries of the new catchment areas mean that families living in the most deprived neighbourhoods have little chance of accessing the most popular schools in the centre of the city."

The study was due to be presented at the British Educational Research Association's annual conference at Warwick University today.

A spokesman for Brighton and Hove City Council said: "We refute the conclusions of this flawed study. The way we allocate oversubscribed schools places is fair and has been endorsed as being fair by the chief schools adjudicator.

"The report is not critical of the use of random allocation but does comment on the catchment areas. However it uses too small a sample of pupils over the first two years and we do not think this is enough to arrive at a firm conclusion.

"Catchment areas in the city have changed since the research was conducted and the report acknowledges that the retained sibling link affects the efficacy of the findings. We are reviewing the system in 2012 as agreed when it was first adopted."