They estimate the woman has got away with thousands of pounds stealing purses, mainly from shoppers in Bon Marche and Oxfam, on Vicarage Road West, in Cleveleys.

The pensioners do not notice at the time as the "purse dipper" is quite skilled, but discover afterwards their property has been taken.

Security cameras have helped police spot the person believed to be the culprit and they are now appealing for the public's help in finding her.

The most recent offence took place on Friday in Oxfam and the same woman was also in the area on August 2.

Officers believe she is responsible for at least three purse thefts in June and suspect she could have been behind a string of similar offences over the last couple of months.

PC Quentin Allen, community beat manager for Cleveleys, said he had received reports of 10 incidents but believed there could be more which had not been reported.

He said: "It has really upset some of the elderly people.

"It's not so much the money, it's quite often that they have personal items of sentimental value, such as photos or other mementos.

"They don't notice the purse being taken, so the dipper is very skilled at what she does.

"It doesn't take place in the street. It's in shops and it tends to be in the same ones – Oxfam, Bon Marche and other charity shops.

"The victims in some cases have known they had their purse as they went into the shop, been in there about five minutes and then discovered it has gone when they have come out.

"We have studied CCTV and seen the same woman in the area around the times of the incidents.

"She is of average height, very thin featured, slim build, she always wears her hair tied up, she has brown hair and has something of an eastern European look or similar.

"We would like people to help us identify her, but also want to warn people in the area to be on their guard and be aware while they are shopping.

"Also we would like to remind people to make sure they do not have their PIN numbers written in pieces of paper in their purse.

"If you can't remember the number, have it altered to something you will remember, like a birthday or anniversary date.

"I would say the offender has probably got away with several thousand pounds by now."

Anyone with information is asked to contact the Crimestoppers hotline on 0800 555111.