Plain-clothed officers targeted more than 50 Portsmouth shops in month-long Operation Steal.
They pilfered £2,500 of goods from stores in Commercial Road, the Cascades shopping centre and Gunwharf Quays in Portsmouth.
The haul included a 6ft ar
tificial Christmas tree worth £56, £129 fur coat and two ballgowns worth £195, and two double duvets costing £800.
Sergeant Rob Sutton, based at Portsmouth Central, said: 'We were quite blatant - we wanted to see what we could get away with.
'With the increase in footfall in the run-up to Christmas we wanted to ensure stores were as ready as they could possibly be.
'It's easy to think you have got all aspects of security covered when you are working in a store, but sometimes it helps to have a fresh pair of eyes.'
The operation was run in conjunction with Portsmouth Business Crime Reduction Partnership and Gunwharf Quays Management.
After stealing the goods police waited outside for security staff. If they didn't arrive officers then took the items back inside.
While some stores failed to spot the thefts, a few did catch police in the act.
An officer was foiled by staff in HMV in Commercial Road after taking two Guitar Hero games from the stockroom.
Police were also caught red-handed when they tried to take a rail of suits worth £1,000 from a store at Gunwharf Quays by staff who ran after them.
And officers were caught out with ladies' belts at Burberry in Gunwharf when the alarm was activated and staff searched their bag.
Sgt Sutton said: 'At Bose in Gunwharf the stock room is so secure it's like Fort Knox, and everything in the shop is purely a display model.
'At other firms we managed to get into staff areas and locker rooms.' Stores where problems were highlighted have now improved security.
Sgt Sutton added: 'The message to those thinking about stealing in Cascades, Commercial Road and Gunwharf Quays is don't bother.
The staff and stores are well prepared, as are the CCTV operators and you never know when a plain clothes police officer is standing right next to you!'
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