Government figures have revealed Sheffield to be the third-worst area in the country for fly-tipping - despite the launch of a council crackdown.
Official statistics showed 21,778 incidents of dumped rubbish were recorded in the city in 2012/13.
The only local authorities with worse records are the London boroughs of Newham and Southwark.
Opposition Liberal Democrats say they believe the continued problem is due to the bin collections change and a cut in hours at household waste recycling centres.
Coun Joe Otten, Liberal Democrat recycling spokesman, said: “These figures confirm what many local residents already know – that fly-tipping is a blight on our city.
“Labour’s complete mismanagement of recycling centres and the move to fortnightly bin collections has only aggravated the problem.”
But Coun Jack Scott, cabinet member for environment, said in fact the 21,778 incidents represented positive news - because during 2011/12 the figure stood at 50,041 pieces of rubbish.
The drop reflects a change in the method of calculating, with incidents recorded now as opposed to each individual item of rubbish dumped. If the old way of recording rubbish was still used, the council estimates around 30,000 pieces of waste were dumped last year.
Coun Scott said: “Overall, fly-tipping is decreasing, which is good news.
“Pilot schemes undertaken on a number of hotspot estates have shown between a 43 and 70 per cent reduction in fly-tipping, and have been welcomed by tenants and residents who live in those areas. We are going to extend this scheme.
“In Sheffield, fly-tipping per person is average, and actually better than many places such as London boroughs, Manchester, Newcastle and Plymouth.
“We’re taking envirocrime seriously, and this year we’ve issued more than 900 fixed penalty notices.”