High Emissions on VW Polo

Hi, Just failed the NCT due to high CO. Results are:
Low Idle: CO - 0.73% - Limit 0.3%
High Idle: CO - 1.01% - Limit 0.2%
Lambda is OK at 1.00

Car is 2006 Polo.

Guy says it smells like its burning oil. Although he did suggest putting in an additive. Don't want to add an additive and fail again. Anyone got any suggestions on the problem.

Thanks.

New cat probably.

My own failed with similar readings. turned out there was a small hole in the exhaust. Mechanic also told me to give the car a good run before i brought it in as if i was only driving a short distance the readings could possibly be high.Passed ok when i brought it back.