Colin Barber wrote to the BBC News website to say he was disturbed to find unattended piles of lost luggage in Heathrow Terminal One.
British Airways says there are delayed bags still at the airport, but they are being monitored by CCTV and are not accessible to the public.
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Following a weekend spent in Ukraine to usher in the New Year, Colin Barber was surprised by the sight that greeted him at Heathrow on his return to the UK.
There were countless bags in the baggage reclaim area at Terminal One.
As far as he could tell, the bags - many of which had labels clearly identifying the owner - were unattended and could have been stolen by unscrupulous individuals.
"A room adjoining the reclaim area was also full with more 'lost' bags," he said, and "in one area there was a pile of about 20 pushchairs".
Mr Barber said he was appalled.
"There was absolutely no security - had I wanted to, I could have picked up any item of luggage, and walked through the green channel.
"No attempt was being made to do anything about the situation.
"There were four BA [British Airways] lost-luggage staff on duty. When I questioned one of them, he said that they were not dealing with the backlog, they were only dealing with passengers missing bags from today's flights."
He added: "Every item of luggage represents a spoilt Christmas/New Year for someone."
Passengers on a number of airlines, such as BMI, Finnair and South Africa Airways, also use Terminal One.
However, British Airways accounts for most of the passengers passing through the terminal and has more passengers affected by the baggage problem than any other airline.
The airline estimates that about 50% of the bags awaiting collection are from its customers, although airport operator BAA suggested it was likely to be a larger proportion.
British Airways apologised to customers who had travelled without their bags.
It said problems had begun before Christmas, when a faulty baggage belt at Terminal Four had led to a backlog.
Fog at Heathrow had led to further difficulties, and there had been another baggage belt problem at Terminal Four on 29 December.
This had all coincided with new working practices for baggage handlers at both Terminals One and Four, it added.
It said: "Our baggage operations at Heathrow have been severely impacted by a combination of events largely beyond our control.
"At Heathrow's Terminal One there are bags belonging to passengers from a number of airlines awaiting collection either by individual customers or by courier companies.
"For customs reasons, they cannot be taken landside to be sorted and remain in the baggage area.
"They [the bags] are all destined for UK addresses. We hope to have them reunited with their owners over the next 48 hours."
But Mr Barber, a management consultant from Brentwood, Essex, disagreed that the fog was to blame.
"The fog cannot be used as an excuse because so many flights were cancelled during that period, the airlines would have had far less bags to handle," he said.
Meanwhile, BAA stressed that the bags could not easily be taken by thieves.
A spokeswoman said: "The bags are being watched by airline representatives in the reclaim area.
"They cannot be taken. They are in an area where they are being watched at all times. They are secure."