THEY outnumber Scots by three to one and total nearly 15 million ... so pest controllers have warned of the dangers of not disposing of Christmas leftovers carefully.

The soaring rat population has increased by three million in Scotland - to 15 million - this year and and pest controllers warned the rat threat was 'extremely high.'

Jenny Rathbone, of UK-wide pest control company Pest.co.uk, said: “The problems are huge. The rat population going into winter was 25% higher than last year, and we are entering a cold period.

“Rats are moving around trying to find food and shelter - many are attacking domestic bins, and anyone being careless about their Christmas rubbish will pay the price.”

Most homes produce more food waste than usual over Christmas, and with less frequent waste collections, bins are overflowing.

Householders are advised to avoid placing any food waste outside of a secure bin. The warning is extended to cardboard and wrapping paper, which make perfect bedding materials for rats seeking shelter.

A recent study showed there are now estimated to be around 2.75 rats per person north of the Border, compared with 2.2 per person in 2019. The figures suggest rats enjoyed a bumper year in 2020, with the vermin “breeding like crazy during lockdown” and making their nests in vacant buildings in quiet streets with poor waste practises.

The study found Glasgow to have the fourth highest estimated rat population in the UK behind London, Birmingham and Leeds, with 1,323,170 believed to be scurrying around Scotland’s largest city. Edinburgh was ranked the UK’s seventh most ratty city, with 1,094,540 of the unwelcome rodents.

Aberdeen is thought to have 487,040 rats while Dundee is estimated to host 327,610. Inverness has 178,350 according to the findings, and Scotland’s medieval capital, Stirling, could have 83,540.

With commercial food sources drying up, it is thought that many rats are now being forced to move towards residential areas.

Further worrying news is that 74% of rats now carry a “hybrid-resistance” to common pest control poisons, which could mean next year rat infestations are harder - or more expensive - to control.

The recent 2019-20 Campaign for Responsible Rodenticide Use survey of rats showed that three-quarters of rats in the UK carried a resistance gene to popular rodenticides, and in some parts the UK, 20% have two different genes, making them super resistant.

Ms Rathbone said: “More and more people are seeing rats in the open - this is a sign that numbers are very high. We are heading for a cold snap, and rats are busy raiding food sources and bedding down. Calls for infestations are already increasing.”

Anyone worried about rats over the Christmas and New Year break should ensure they do not leave any food waste unprotected. Any excess rubbish containing food of any sort should be kept secure, with no bags left outside of a bin, especially Christmas dinner leftovers.

Pest.co.uk also advise householders to consider placing a brick or heavy object on top of their wheelie bin; keep all areas of your home clean and tidy; block up any gaps or holes in brickwork; and remove cardboard and wrapping paper as these form ideal bedding materials for rodents.

Spokeswoman Ms Rathbone added: “The advice is really simple - do not leave any Christmas waste in the open or outside a secured bin. Do not, under any circumstances, leave any Christmas food waste inside your home, as the rat threat level is currently extremely high.”