Properties are being routinely mis-measured by estate agents, it has been claimed.

The firm behind the allegation, Spec, provides technology which it says provides accurate property measurements for floor plans.

It says its uses software and laser scanners that comply with RICS standards.

Comparing measurements and plans of 304 properties in London with its own technology, Spec says that one in eight had a discrepancy of at least 100 square feet, while the average discrepancy across all properties was 54 square feet.

In most (60%) cases where there was mis-measurement, the size of the property was over-stated.

Anthony Browne, senior adviser to Spec, said: “This is the great hidden scandal in the property market.

“It is ridiculous that when you buy a pint of beer or a pound of sugar you know exactly what you are getting, but when you buy your home you don’t.”

Spec’s ‘white paper’ on the subject was put together by university researchers from London and Cambridge.

It cites cases adjudicated by both The Property Ombudsman and Property Redress Scheme where different agents measured the same property differently.

In the TPO case, three different agents measured the same property as being between 664 sq ft and 745 sq ft. In the PRS case, compensation of £1,000 was paid after a buyer complained that one agent’s floor plan was 25% larger than another’s.

The report says that one of the properties looked at by researchers was being marketed as 3,229 sq ft, when it was actually 2,808 sq ft.

It says that the difference in value, based on £626 per sq ft, was £263,546.

In another case, a property was marketed at 1,455 sq ft but was found to be larger, at 1,684 sq ft.