Starbucks is charging an additional 5p for disposable coffee cups in 25 London stores as it seeks to explore the impact of a levy on consumer behaviour.

The trial will run for three months and is being supported by a prominent marketing campaign for its £1 reusable cups, which secure customers an automatic 25p discount.

All the money raised by the disposable cup charge will be donated to Hubbub, environmental charity and behaviour change experts, which will run a behaviour change study to help it to understand how the public can be encouraged to choose reusable drink containers.

“At the same time, we will redouble our efforts to ensure that drink-in customers are always offered a ceramic cup, thus cutting paper use even further,” a spokesman for Starbucks said.

“In 2016, as a way to heighten awareness and to promote reusability we extended the reusable cup discount to 50p for a few months. We found that this did not move the needle in the way we thought it might. We now have 1.8% of our customers using reusable cups,” the spokesman added.

An estimated 2.5 billion disposable cups are thrown away in the UK each year.

In January a report by the Environmental Audit Committee called for a 25p tax on disposable coffee cups to be used to improve the UK’s recycling and reprocessing facilities.

The cups cannot be recycled through normal systems because they are lined with plastic which is difficult to remove.