Police officers should be banned from accepting free tickets to high-profile events such as Wimbledon, the FA Cup Final or pop concerts, inspectors said today.
Sir Denis O'Connor, the chief inspector of constabulary, said accepting such hospitality risked creating the perception that police officers had conflicts of interest, damaging the service's reputation in the eyes of the public.
His comments came as a review by Her Majesty's Inspectorate of Constabulary (HMIC) found that while corruption was not endemic, there was a "hugely inconsistent approach" across police forces in their attitude towards free gifts.
Asked whether officers should be banned from accepting free hospitality at key events, Sir Denis said: "Clearly it is for the police service, encouraged by the Home Office, to come up with standards.
"But I would have thought, in the circumstances, unless there's a very clear public benefit, not personal benefit, it would be very strange indeed to be carrying on with that kind of behaviour.
"It leads to perceptions that you may have a conflict of interest."
Roger Baker, the inspector who led the review of police relationships, said: "You've got to be very clear on the reason why you want to accept tickets to the FA Cup Final, or something like that, and there are major perception issues.
"Let's take pop concerts. The staff working in the police service were very clear that they found that was not acceptable.
"Public servants thought that was very, very iffy.
"And so unless there's a really good reason which I can't think of, then the answer to that should be 'No, don't'."
He said the inspectors were "keen to get clear guidance on what is acceptable and what isn't".
"Instead of just picking out pop concerts, and 'Do I go to Premier League football matches?', or whatever it is, there needs to be a consistency across the police."
But Mr Baker added that "no one is suggesting you can't have a cup of coffee".
The review said officers recognised that the public might wish to show their appreciation following an interaction with the police, saying that "a box of chocolates was seen as entirely acceptable, whereas an invitation to attend a sporting event or pop concert was felt to be unacceptable".
It added: "We found numerous examples of senior officers accepting hospitality from suppliers and others who were tendering for business.
"In a number of forces, for instance, concert and premier sporting event tickets were accepted from companies which were tendering for business or had been successful in tender.
"Whilst this hospitality had been recorded, it could be viewed, by some, as being inappropriate."
Mr Baker said: "While we found no evidence of endemic corruption in police service relationships, we did find significant variations between forces and authorities in how they defined what is acceptable and what is not.
"This inconsistency made little sense to us and nor do we believe would it to the general public.
"There are no geographic boundaries when it comes to integrity and there should not be local differences in standards."
The HMIC report, Without Fear Or Favour: A Review Of Police Relationships, found that while major contracts were professionally managed, "checks and balances are less evident on spends of around £5,000 and under".
Only 20 of the 43 forces in England and Wales gave staff clear written guidance to help them decide whether to accept or decline a gift, with 15 placing an acceptable value on gratuities of between £5 and £75.
"All forces and authorities have a recording mechanism for gratuities and hospitality: but these are not consistently completed in most cases," the report said.
"There are many examples of departments and BCUs (basic command units) not recording anything at all (even though focus groups and interviews confirmed that hospitality had been received).
"There is also evidence of officers recording the receipt of gifts in their pocket books rather than in the formal registers."
Mr Baker said there was "an urgent need for a wake-up call for the police service and its leaders".
The police needed to recognise that it was not just important to act fairly, but also to be seen to be acting fairly, the report said.
The lack of controls, not always considered as corruption, can allow a slippery slope to develop.
The report also considered relationships between police and the media in the wake of the phone-hacking scandal.
The inspectors called for forces and authorities to record "all interactions between police employees and media representatives", saying that most forces were too complacent, adopting the attitude that "it would not happen here".
It found most forces thought concerns around inappropriate relationships with the media were only a problem for the Metropolitan Police in London.
There was also "little clarity about the boundaries of acceptability" in relation to corporate entertaining with the media, with many forces relying on a commonsense approach.
The report said: "We found that forces lack the capacity and capability to proactively identify any inappropriate relationships.
"Forces conveyed a sense of inevitability that resourcing complex investigations into media leaks rarely yields any positive results.
"Forces should explore options for identifying and monitoring emerging and inappropriate relationships with, and leaks to, the media."
The 14-week review was ordered by Home Secretary Theresa May in July.
Chief Superintendent Derek Barnett, president of the Police Superintendents' Association, said the lack of clear and consistent guidance over gifts and hospitality "should be addressed as a matter of urgency".
"Strong and clear leadership is essential in promoting an ethical police service and ensuring that all police officers and staff act within the law and to uphold the strong reputation that we have for honesty, integrity and impartiality," he said.
He added it was "a matter of critical importance that the police should not only act fairly, they must also be seen to act fairly".
The Association of Chief Police Officers (Acpo) added that while the review showed there was no "systemic corruption", individual officers were letting their colleagues and the public down.
Paul McKeever, chairman of the Police Federation, which represents rank-and-file officers in England and Wales, also said the development of clear national standards was "hugely important for the future integrity of the police service".
Mark Burns-Williamson, chairman of the Association of Police Authorities, added: "Across a range of issues which could cause concern, the public will expect common sense to prevail and clear standards to be enforced with consistency."
Mr Baker also raised concerns over the 5,400 corporate credit cards in circulation in police forces around the country, which he said could potentially run up a total bill of £200 million if they were all maxed out.
"There will be a tiny number of people in any organisation - particularly in these times of austerity - who could be tempted by 'Shall I use the card for something other than a legitimate purpose?"' Mr Baker told BBC Radio 4's World at One.
"We have previously seen cases of that in policing, where there have been inquiries. I'm not suggesting that everybody is out there using their corporate credit card for ill, but there need to be clear governance and oversight procedures."
Staffordshire Chief Constable Mike Cunningham, who speaks for Acpo on professional standards, told The World at One: "The headline of the report is that there is no evidence of endemic corruption.
"There are clearly issues that the HMIC inspection has raised and set out very clearly, but I don't think it is something that the service responds to with disappointment."
Police services should reconsider their guidance on gifts and hospitality, and it may be that officers should be told they should not accept them at all, said Mr Cunningham.
"The public do have, quite understandably, some difficulty with some of the gifts that police officers have taken," he said. "The service needs to look very carefully at the guidance it gives.
"What is the public benefit in an officer receiving a gift of any description and what is the personal benefit? If there is no public benefit, then I think the public could quite properly question the decision to accept any gift or any hospitality."
A Home Office spokesman said: "The integrity of forces is critical to public trust in policing.
"The vast majority of officers behave appropriately, but we need to ensure that all forces are operating to the standards of the best.
"Forces need to set clear standards and ensure that the rules are followed. This report will help them to do so."