Dozens of police forces have made out-of-court settlements totalling more than £30m in the past four years, according to recent figures, which were described as “the tip of the iceberg” in terms of people on the receiving end of unlawful police behaviour.

Payments range from small sums for loss of property, or the £100 paid by Sussex police for “embarrassment and humiliation”, through to hundreds of thousands of pounds paid for wrongful arrest, records revealed under the Freedom of Information Act show.

The Metropolitan police were responsible for the lion’s share (£19.6m) of the settlements. Of that, the force paid £7.9m to settle 479 claims categorised as being for “malfeasance”.

The FOI figures did not include the large amount of legal costs that police forces had to also cover, pushing the figures still higher.

In a climate of increased scrutiny of police conduct, experts said the disclosures indicated inconsistent standards and inadequate accountability mechanisms.

Mark Stephens, the lawyer for the former Conservative MP Harvey Proctor, who has been awarded £500,000 in compensation by the Met after their bungled investigation into allegations of a VIP paedophile ring, warned that the figures revealed wildly differing standards in how police forces dealt with complaints and that some forces appeared to fight even difficult cases “to the bitter end”.

“The Metropolitan police is known for picking the fights that they are going to win and settling the cases they know they will lose, with a little margin in between,” said Stephens, of the firm Howard Kennedy LLP.

“Then if you take a force like Sussex, they fight everything to the bitter end, incur huge legal costs – which are a complete waste of money because the victim wants compensation and a settlement, while the only people who gain are the lawyers.

“You tell the client going in this is what they are going to do in response, and we know that this particular police force behaves in this ridiculous way … as a consequence we are likely to issue a writ, which is likely to cost up to £10,000 just for the fee.

“So there is £10,000 for every writ that is issued, because they have not entered into sensible and meaningful negotiations, nor do they enter into mediation or dispute resolution, which might obviate the need to incur legal costs.”

Dr Waqas Tufail, a senior lecturer in criminology at Leeds Beckett University and co-founder of the Northern Police Monitoring Project (NPMP), said that existing accountability mechanisms, whether internally within police forces or those of the Independent Office for Police Conduct (IOPC), were clearly not effective or robust enough.

“Questions should now be raised as to the extent to which police forces are using compensation in order to protect both their reputations and to protect officers who who may have abused police powers,” he added.

As well as the Met and Sussex, 32 other UK police forces provided figures, including additional detail on payouts. More than £800,000 in payments have been made in the past four years by Thames Valley police, which included more than £300,000 for 60 cases categorised as being for “injury/loss liberty/reputation” following arrests. The largest payouts in that category were one for £30,000 and three for £20,000 each.

Like other forces, dog bites led to five payouts by Thames Valley, which included two £10,000 each last year. Sussex police paid out £878,777 in the past four years, including one payment of £128,349 for negligence and one for £5,500 for data protection failures. Others included seven for false imprisonment, with one for £15,000 and another for £13,500.

Elsewhere, the £63,000 paid by Gwent police in the past four years included a £10,000 payment following a breach of the Data Protection Act. The £420,000 figure for Police Scotland included cases such as £2,000 for “alleged failure to investigate” and £12,000 for “alleged used of excessive force”.

Some forces refused to reveal their out-of-court settlement figures in response to the Guardian’s request by saying it would be too costly or, in the case of Greater Manchester police, failing to provide any reason why they could not. Cambridgeshire constabulary said they could not do so because they had “outsourced” their legal team.

Dr Joanna Gilmore, an academic at the University of York’s Law school and a co-founder of the NPMP, said the overall figures “were likely to be the tip of the iceberg in terms of those who have been on the receiving end of unlawful police behaviour”.

She added that it was increasingly difficult to access legal aid to bring a civil action against the police, and that access to specialist legal advice could be difficult to obtain, particularly outside London.

“The reality is that most people who experience unlawful police behaviour do not bring a civil action against the police,” said Gilmore, whose own research on protest-related cases had shown it could take years to settle claims.

The Met did not respond to a request for comment.

Sussex police said: “Every claim that is received by Sussex police, whatever its value and circumstances, is fully and objectively investigated by a dedicated civil claims team.

“Where any liability exists, we work with claimants to ensure a fair and as swift as possible resolution to their claim, also ensuring that the public purse is protected from disproportionate, unreasonable and sometimes false claims. More often than not, this does not require the intervention of the courts, as shown in the figures for 2016-2019 – 21 cases settled in court, compared to 332 outside.

“If no liability exists, it is right and correct that it should be defended robustly to ensure only claims that have merit are settled at the cost of the taxpayer.”

Among other forces who have spent significantly on out-of-court settlements since the beginning of 2016 were Lancashire constabulary (£1.96m), West Midlands police (£1.7m) and Warwickshire police (£1.19m).