Charles and the premier have had several discussions about modern housing developments since Labour leader Starmer took office in July, according to officials.

Starmer has said he wants to build several new towns as part of his ambition to ease Britain’s housing crisis and aims to construct 1.5 million homes by 2029.

The duo and deputy prime minister Angela Rayner visited Nansledan, a new housing development outside the seaside town of Newquay in Cornwall, southwest England.

It was developed by the Duchy of Cornwall royal estate when Charles, a keen environmentalist, was heir to the throne and in possession of the duchy and the Duke of Cornwall title, now held by his son Prince William.

Construction started in 2014 and some 1,200 people currently live there. The entire project of 4,000 homes, shops, restaurants, offices and health facilities is expected to be completed by 2045.

According to its website, the area is “land-efficient, reflects local identity using low-carbon materials, is less car-dependent, and is affordable and accessible to local people and businesses”.

Charles showed Starmer and Rayner a school and an orchard during their visit.

Monday’s visit is believed to be the first time in decades that a politically neutral monarch has been accompanied by the prime minister and deputy prime minister on a royal engagement.

In 1998, then prince Charles invited and took then deputy prime minister John Prescott on a tour of his similar Poundbury development on Duchy land in Dorset.