Picnics during long walks are legal but sitting on a park bench for lengthy periods may violate the coronavirus lockdown, according to new police guidance.

It confirms that people can buy “non-essential items” from supermarkets, but cautions against leaving the home for DIY supplies.

The document states that the Health Protection Regulations 2020 “specify maintenance and upkeep”, and that going out and “buying paint and brushes, simply to redecorate a kitchen” would be illegal.

Amid continued confusion over what is a “reasonable excuse” to be outside under the new law, the Crown Prosecution Service has drawn up examples of potential cases.

Despite police forces telling people not to travel to national parks and beauty spots, the CPS confirmed it is “lawful to drive for exercise” and to exercise outside more than once a day was likely to be reasonable.

But the document, which was published last Thursday, and applies to England only, said “far more time [should be] spent walking than driving” in order for the journey to be lawful.

“Stopping to rest or to eat lunch while on a long walk” is also deemed reasonable, but a “short walk to a park bench, when the person remains seated for a much longer period” is not.

“It is acceptable for a person to stop for a break in exercise,” the document states.

“However, a very short period of ‘exercise’ to excuse a long period of inactivity may mean that the person is not engaged in ‘exercise’.”

Police on horseback talk to a man in Victoria Park in London, Britain (EPA)

The guidance, which has been published by the College of Policing, said that people are able to leave home for work even if they are not a key worker “where it is not reasonably possible to work from home”.

Following numerous reports of police demanding identification from NHS staff, the document says: “Police should not ask for ID documents or any other kind of document.”

It added that there was no legal requirement for people to carry written proof of their need to travel for work or volunteering.

“Moving to a friend’s address for several days to allow a ‘cooling-off’ following arguments at home,” was among other reasonable excuses listed.

The Health Protection Regulations 2020 are separate from government guidance and less strict in some respects.

Parliament’s Joint Committee on Human Rights warned that police may be punishing people “without any legal basis” because of confusion caused by the differences.

The law does not define “essential travel” or say how many times people may exercise outside a day.

Instead, it states that: “During the emergency period, no person may leave the place where they are living without reasonable excuse.”

The legislation gives a non-exhaustive list of reasons, including exercise, obtaining “basic necessities”, caring for vulnerable people or working if it is not possible from home.

The law allows officers to arrest people for breaking restrictions on movement and gatherings, or fine them up to £960 for repeated offences.

Police apologise after reprimanding man for being in his front garden

More than 3,200 fines have been issued across England so far, with most being handed out on days that saw warm and sunny weather.

Senior officers said 39 fines that were wrongly handed to children would be rescinded.

The law did not come into force until three days after Boris Johnson announced the UK-wide lockdown on 23 March, and police forces in different areas have taken different approaches.

Some were accused of going beyond the law when suggesting that shopping trolleys could be policed and telling people they could not sit in their own gardens.

Police leaders have been attempting to improve consistency amid concerns that the relationship between officers and the public will be permanently damaged.

Two forces have so far admitted wrongfully charging people under the Coronavirus Act 2020 – a separate law drawn up to enforce planned quarantine and testing measures that were not implemented.

Martin Hewitt, chair of the National Police Chiefs’ Council, admitted that there had been “mistakes” but said police officers were “trying to do their best in very difficult and unusual circumstances”.

“Where there have been examples where we’ve seen officers going a bit too far to get the message across, we have been public about the fact that was not what we wanted,” he told a press conference this week.