In our Crime on Your Street series DAVID LEASK looks at what has caused such a major increase in the figures.

SENIOR officers are increasingly concerned by the number of minor sexual assaults both in streets and clubs.

As figures for rapes and attempted rapes hold steady, Glasgow's overall level of sex crime rose by another 16%, from 904 in 2010-11 to 1055 in 2011-12.

That bucked trends for violent and other crimes, which have dropped to levels unseen since the early 1970s.

But in the city centre – the area bounded by the M8 to the north and west, the Clyde to the south and the Saltmarket to the east – sexual offences, including bottom-pinching and groping, have shot up nearly 48% in 2011-12.

Val Thomson, the chief superintendent responsible for policing the city centre and West End, said: "We have seen an increase in indecent assaults by strangers within the city.

"By that I mean women walking down the street and being touched on the breast or bottom by somebody walking past."

Police are trying to figure out who is behind the offences, which are more stereotypically associated with southern Europe than Scotland but are not jumping to conclusions about the nationalities of perpetrators – especially as one recently caught prolific offender was Scottish.

Ms Thomson said: "We are looking at the profile of the offenders involved because it is not something we've experienced before.

"Or, is this something woman have experienced before but have not reported? We need to get a better understanding of this.

"Is it foreign nationals who are committing the crime? Or has the indigenous population been involved in that kind of crime for a long time but it has not been reported?"

NIGHTCLUBS take an increasingly tough stance on male customers who make women uncomfortable on the dance floor.

And they immediately call the police if women are groped.

Several perpetrators have been caught in clubs – one recently after being detained by stewards and another who was recognised by staff when he returned to a venue where he had previously assaulted women.

Men found guilty of groping – and CCTV makes this relatively easy – can end up on the sex offenders' register. Detection rates for indecent assaults are currently around 70%.

Ms Thomson, however, is eager to encourage reports of such crimes, because it helps police identify men whose offending may become more dangerous.

She said: "This kind of offence is getting reported to us before it becomes serious sexual crime. That is giving us the chance to investigate and identify somebody responsible for it – and to deal with the offending individual before it escalates.

"It is rare for someone to commit a 'stranger rape' as a first crime. We want the reporting at the 'lower' level. But I don't mean to diminish indecent assaults like this, because they are horrible crimes."

There were 192 sex offences recorded in the city centre in 2011-12, up from 130 the year before and the highest figure since the Evening Times began its Crime on Your Street series in 2006-07.

The city-wide figure at 1055 was also the highest in the last six years.

AGROWING number of reports of groping and bum-pinching are not the only reason sex crime figures are rising.

Historic abuse cases and mass hauls of child porn are also driving up the statistics. The number of rapes does not seem to be going up, at least in the city centre, despite a horrible spate of attacks in the run-up to Christmas last year.

For example, Ms Thom-son's division – which stretches from Saltmarket to Drumchapel – had 44 rape reports in 2011-12, compared with 42 the previous year and 45 the year before.

Police had expected a rise in rape reports since the definition of the crime has widened in recent years.

Strathclyde Police this month announced a special force-wide unit to try to boost the conviction rate for rape.

Crucially, they said they would employ female civilian advocates to support victims, using techniques that have proved successful in domestic abuse cases.

Outdoor 'stranger danger' rapes – despite the brief spate last winter – remain extremely rare.

The last in Glasgow city centre was by Scott Kerr, a man who sexually assaulted one woman before raping another in December last year. Kerr, from Dundee, was jailed for 10 years.

25 CRIMES TOP THE LEAGUE

:: Hillhead came out joint top of the unofficial table for beats with the most sex crimes, with 25 in 2011-12.

This was almost entirely down to three offenders flashing at students in back courts and committing acts of indecency. There were only seven sex offences recorded in the beat in 2010-11.

:: The beat called Alpha Bravo 6 by police –Buchanan Street South and Argyle Street – was Glasgow's overall busiest last year and joint top with Hillhead in the sex crime league table, with 25 offences. It had 21 in 2010-11.

:: Because sex crimes are relatively rare, a spate of incidents by one offender – or even a person accessing child porno-graphy – can skew beat data. Springboig and Easterhouse, for example, are in the top 10 in 2011-12, despite previously low levels of offending.