The number of litter fines issued by councils has almost quadrupled in six years, with more than 250,000 handed out last year.

The rise coincides with a growth in the number of local authorities in England and Wales employing private companies to police the streets for littering.

A freedom of information (FoI) request from the civil liberties group Manifesto Club found that 250,676 fines were issued in 2018, 86% by private companies.

The group said private wardens had an “incentive to issue as many fines as possible” because their employers were often paid per fine.

A previous FoI by the group found that 63,883 litter fines were issued in the year 2011-12.

The number of councils employing contractors, including Kingdom Services Group and 3GS, has also soared in the past few years.

In January, a Guardian investigation found councils were making millions of pounds from Kingdom Services Group. The private company was accused of using aggressive and intimidating tactics to issue fines for minor offences such as littering and dog-fouling.

Kingdom has in the past also been scrutinised over its tactics when issuing litter fines. One person claimed they had received a £75 fine after accidentally dropping a piece of orange peel the size of a 10p coin.

Between 2011 and 2012, 13 councils employed private companies to issue fines. This rose to 46 councils by December 2016 and 73 last year.

Manifesto Club, which campaigns against the “hyper-regulation” of public spaces, said it believed outsourced issuers led “to the inevitable corruption of punishment”.

It said: “Wardens will not issue fines in the public interest, targeting the more serious offences, but instead will focus on ‘easy targets’ or even non-offences that will generate the greatest income for the company.”

Bristol city council issued the most fines for littering offences last year, 9,851. The council employed Kingdom until February 2019 and now employs 3GS to enforce littering laws and public space protection orders (PSPOs).

PSPOs can be issued to deal with nuisances, such as prohibiting the consumption of alcohol in certain places or forcing someone to keep their dog on a lead at all times.

Data also showed that people living in areas where their council employed a private company to issue litter fines were more likely to be fined than in areas using public officers.

The councils employing a company to issue litter fines in 2018 issued a combined total of 214,646 fines – an average of 2,940 per authority. The 230 that used employees to issue fines together issued 36,032 last year – an average of 157 per council.

In April last year, the government increased the amount councils in England could fine people for dropping litter, including from vehicles, from £80 to £150.

A government spokesperson said: “Littering is a significant issue for residents and has many hidden costs which can restrict local economic growth as well as harming pets and wildlife.

“While it is the responsibility of councils, we have been clear they must not abuse the power to impose penalties, and should take into account local circumstances, such as the ability to pay.”