Camden Council spent nearly £800,000 on fly-tipping in 2018-19, nearly double its previous year’s outlay.
Camden Conservatives has called on town hall figures to "take their heads out of the sands and clean up our streets", but the council insists its introduction of the Clean Camden app in 2017, which allows people to report fly-tips online or via their smartphones, has increased spending only because more residents are better able to report dumps.
BBC research recorded the number of fly-tips in Camden - which were all small-scale - at 25,765 during 2018-19, costing the council £791,441.
This compared with a total of 12,170 incidents in 2017-18 and a cost of £405,871.
Camden Conservatives leader Oliver Cooper criticised the figures, saying: "Labour have never taken the filthy state of Camden's streets seriously.
"They ridiculed the idea of introducing fines for fly-tipping when I proposed them, right up until they realised the public wanted tougher action.
"And now they refuse to use their own eyes and see the state of our streets and claim fly-tipping isn't increasing at all.
"It's time they took their heads out of the sands and cleaned up our streets."
Government figures released in November showed Camden was second only to Leeds in the UK for the number of fly-tips, with West End Lane a known hotspot.
Camden Council environment chief Adam Harrison said: "In 2017 we introduced the easily downloadable Clean Camden app, which allows residents to report a flytip directly to us, which we can then promptly come and clear.
"A consequence is that making this easier has increased the number of reports we receive.
"At the same time, we know that fly-tipping across the country has gone up, as irresponsible people use and abuse public spaces for their own private gain."
Cllr Harrison added those caught fly-tipping stand to be fined up to £400, with Camden last year issuing 114 fixed penalty notices, 945 statutory notices and 16 successful prosecutions for waste offences.
He also pointed to an audit by Keep Britain Tidy which suggested "strong improvement on previous years".
West Hampstead Amenity and Transport chair John Saynor agreed the Clean Camden app helped deal with fly-tipping, but believed greater education and communication was needed.
"It's education, education, education," he said.
"To address this problem the council needs to make sure people understand the system and explain in the simplest language what people should do with their rubbish."
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