That is the exact question that left legal experts scratching their heads after a woman complained about a taxi driver relieving himself in Bournemouth town centre.

The woman rang the Town Hall after witnessing the act, but claims she was told that while urinating in public was an offence, no action could be taken against the driver because of an obscure law dating back more than 100 years.

Ashley Miller, chairman of the Bournemouth Taxi Association, said: "The Town Police Clauses Act of 1847 said that a hackney carriage driver could urinate against the rear offside wheel . That is still in place today.

"The law goes back to the days of the horse and carriage. People used to ply for hire and there were no public toilets, so they would get out and pee on the back wheel. It's not known by everybody.

"Of course drivers shouldn't be doing it in public because it doesn't get us a very good name. I live pretty centrally so I can always go home, and for those of us who work at the railway station, the toilets are normally open there. Quite a few of us have keys for the disabled toilets.

"There shouldn't really be a need for anybody to urinate in public, but for every taxi driver that does it, you've got about 15,000 members of the public who do it everywhere and anywhere."

Roger Hall of Dorset's Crown Prosecution Service said people caught urinating in the street could usually be prosecuted under the Public Order Act, but it appeared hackney carriage drivers might be exempt.

Rob White, group manager at Bournemouth council, told the Daily Echo: "We will be looking into the relevant law to deal with this matter. We have not had a similar report of this nature in the past, therefore we have had no need to look at this particular area before.

"However, now we will be checking the law thoroughly and we will be making any representations if we feel it needs to be changed. As a council, we agree this is not appropriate behaviour by anyone."

The council confirmed that a licensing officer would also be speaking to the driver concerned.

In a final twist, a spokeswoman for the government's transport office told the Daily Echo: "Our legal people have had a look through all the old legislation and can't find any such law."