St Albans has once again been named the top UK city for adulterous relationships.

The UK’s largest married people’s dating site, Illicit Encounters, has found that 5,631 supposedly monogamous people are having an affair in St Albans - 2.74 per cent of the population.

That is up from 5,015 cheaters last year and is a 12 per cent increase in 12 months.

In 2017 St Albans was named on this Infidelity Index as the Hertfordshire capital for love rats, but the city rocketed up the ranks in 2018 to bag the top national spot and remains the reigning champion for 2019.

Illicit Encounters spokesman Christian Grant said adultery is “booming”: “Lots of couples in Hertfordshire cannot afford to divorce due to the cost of establishing two new homes, so they are sticking with their partner and adding some spice to their marriage by discreetly having an affair.

“They know that with a site such as Illicit Encounters they can have an affair with a like-minded partner who is also looking to cheat.

“Both sides can have some fun without upsetting things at home.”

Other top ranking places include Oxford, Bath, Gloucester, Durham, Exeter, Lichfield, Peterborough, Inverness, and Newcastle upon Tyne.

Since its inception 16 years ago, more than one million people have registered with Illicit Encounters and it estimates that each week about 20,000 people are conducting affairs on the site.