The number of children aged between six and 16 who do not have a swimming certificate has more than doubled in the last five years, and ethnic minority children are the least likely to be able to swim, figures from the Mulier Instituut have shown.

The sport research institute found that last year some 13% of children had none of the three certificates, which denote the different levels of ability – more than double the 2018 figure.

Income is a determining factor, the institute said, with a quarter of children from the poorest families having no certificate at all, compared to just 2% of children from richer households.

Children with an ethnic minority background are also less likely to have a swimming certificate. Some 28% of children in this group have no certificate at all but this drops to 18% for minority children whose parents were born in the Netherlands.

According to statistics bureau CBS, ethnic minority children have a nine to 10 time greater chance of drowning. This summer, two children drowned in one week, one a six-year-old born in Turkmenistan, the other, a nine-year old from Afghanistan.

Swimming lessons for primary school children are free but there are subsidies in place for older children.