Sally Magnusson presented the series which was broadcast in March

The broadcasting regulator received 58 complaints about the four shows in the Britain's Streets of Vice series.

Among the issues covered were brothels, pornography and drug-taking.

The BBC said care had been taken before it was aired, but any plans to cover sexual themes in the daytime schedule would be heavily scrutinised in future.

The majority of complaints to Ofcom concerned the final programme in the series, which dealt with pornography, and featured interviews with a dominatrix and a porn star.

The BBC received more than 200 complaints from viewers following the transmission in March.

Strength of content

The series came as the BBC changed the emphasis of daytime schedules to include more informative, issue-led programming.

In responding to the Ofcom investigation into Britain's Streets of Vice, the BBC said discussions of a sexual nature were nothing new to daytime TV and had been widely covered by daytime talk shows.

Although there were on-air warnings before the programmes aired, Ofcom decided that these had not prepared viewers for the strength of the content at that time of day.

Although the BBC had scheduled the programmes during term-time to avoid children watching, Ofcom stated that heavy snowfalls had closed some schools that week, highlighting the potential risks.