The lead-up to Valentine’s Day is an ideal time to catch out cheating partners as they try to satisfy both their spouse and lover, private investigators say.

They claim the weeks before February 14 are when cheaters leave most evidence of their affairs, such as receipts for romantic gifts or suggestive texts.

Many private investigators say that in the past few years the number of people looking for proof of their partner’s infidelity has surged.

Some believe it is because of the high numbers of divorcees who do not want to be fooled by subsequent lovers.

Wellington’s Rokez Investigations director Kerrie Pihema said Valentine’s Day required extra effort on the part of adulterers to satisfy their love interests.

Pihema, a former policewoman, said giveaway signs of affairs were additional time spent texting or emailing, particularly if the partner was unwilling to share information about what they were doing.

Other tell-tale signs were a flurry of activity on the credit card, unexplained cash withdrawals and lots of disappearances to urgent meetings, she said.

While these things could also be the behaviour of a faithful lover planning a Valentine’s surprise, those paired up with an adulterer usually knew the difference.

“We find by the time they (clients) come to us they are pretty certain something is going on, they just want proof. As they say, where there’s smoke there’s usually fire.”

She advised those who suspected their loved one was a rat to be vigilant for tell-tale signs, record their suspicions and talk them over with a friend.

Pihema said a few years ago she received a couple of calls a week about investigating infidelity but now got about six enquiries a day.

About 60 per cent of clients were men and they usually earned over $100,000, Pihema said.

The rise of internet dating, which allowed people to create fictitious profiles and make contact with hundreds of singles, made adultery easier, Pihema said.

Christchurch private investigator and former police detective inspector Dave Haslett said “relationship issues” were becoming an increasing focus in his industry.

Joanna G lingerie store owner Mick Dore said it was common for them to sell two sets of underwear to customers for Valentine’s Day.

“One set gets paid for with the credit card for the wife and the other gets paid with cash for the ’secretary’,” Dore said.

The cheating customers usually bought different kinds of lingerie for their wife and their mistress, he said.