The number of new but "unabsorbed" houses has spiked in Calgary, according to a new report by ATB Financial.

Unabsorbed houses are newly-built single and semi-detached houses that don't have a binding, non-conditional agreement in place yet for their purchase or rental.

There were 27 per cent more of these properties in Calgary on the market than last year, according the report's authors Todd Hirsch and Nick Ford.

A high number of new and vacant homes could have a negative effect on prices and slow the construction industry at a time when it's already suffering, the two economists say.

"Unfortunately, it's likely that we will continue to see unabsorbed housing push higher, especially in Edmonton," the report says.

Alberta's capital has seen an even more drastic rise, reaching a record-high of 66 per cent. The trend is another indication that the downturn in the energy sector is dragging down the housing industry.

Housing starts in Alberta are down 56 per cent from last year.