Planners had stalled the former prime minister’s addition to the moated, grade II listed property over fears for the protected creature.

A South Oxfordshire District Council planning officer had warned that the presence of newts nearby could be impacted by the development. He advised planning permission should not be granted, without an assessment.

Under council rules, potentially harmful developments can be approved if improvements to the natural environment are found elsewhere, resulting in a net gain for biodiversity.

Mr Johnson and his wife Carrie have now proposed to dedicate the pool to them or build a “little newt motel” in what he described as a “newtopia”.

The Johnsons agreed to bolster an orchard area of their garden by planting young trees, creating deadwood habitats and better managing the existing trees.

Great crested newts, which measure up to 17cm long and are black with spotted flanks and an orange belly, are protected under British and European wildlife law. Their numbers are in decline, with habitat loss being their biggest threat.

Outlining the approval for the Johnsons, the planning officer Tom Wyatt wrote: “The proposed pool will result in the loss of a small area of garden area. It is proposed to enhance an adjacent area of orchard to compensate for this small loss and deliver an overall net gain for biodiversity. The council’s countryside officer [Church] has no objection to the proposal on the loss of biodiversity subject to a condition.”