The National Landlords Association reports that fully 74% of calls to its helpline are currently from members worried about how to deal with the effects of tenants not paying their rent.

They have good cause to worry as unemployment rises month by month, it is inevitable that an increasing number of tenants will struggle to find the rent. The knock-on effect, of course, is the equivalent of the dreaded void - and that can leave landlords with significantly reduced yields and struggling to meet mortgage payments.

The NLA says it has received over 30,000 individual calls in the past 12 months - an average of 2,500 a month - of which 74% were from landlords after advice on how to deal with tenancies when rental arrears begin to build.

Arrears and repossessions in the buy-to-let market have both risen sharply, says the association.

Richard Price, director of operations at the NLA, said: "No landlord wants to serve notice on a tenant, but the reality is that landlords are forced to do this when rental arrears becomes serious."

So, why do tenants stop paying rent and what's the answer for landlords?

The reasons are not always as obvious as many people expect. What matters, though, is that action is taken rapidly to prevent the situation escalating and creating unmanageable consequences.

And one way of taking action is to do so BEFORE the problems start - getting informed about eviction processes AND going to the trouble (and expense) of taking out rent guarantee insurance, which is growing increasingly popular among landlords.

Legal and rent protect policies are now widely available and can often be tailored to precisely the kind of protection a landlord wants and is willing to pay for. Generally, though, the old adage applies: you get what you pay for.

Comparisons between policies are difficult, because very few offer exactly the same kind or levels of protection. Some offer simple rent protection, others package this with buildings and/or contents insurance and perhaps legal costs cover.

Whatever product is selected, the provider should be authorised and regulated by the Financial Services Authority (FSA).

As experienced buy-to-let landlord Tony Booth says, "A good legal and rent protection policy takes away the hassle by varying degrees.

"The better ones remove the problem completely by reinstating rent payment arrear amounts and acquiring vacant possession of the property; while others may only protect against the worst-case scenario, such as covering a short period of arrears while you hire a solicitor to get possession proceedings get underway.

"These policies offer more than a continuity of rental income, they take away the fear and apprehension of uncertainty," added Tony, who has been in the BTL business for 30 years.

"Legal and rent protection policies allow landlords to feel confident that regardless of rent arrears or an incumbent bad tenant, rental income will continue unabated so that monthly mortgage payments can be met - and someone else will deal effectively with the complex legal procedure of removing the defaulting tenant from the property."

And, of course, in the current economic environment, even a good tenant can suddenly find themselves struggling, most likely due to the loss of a job.

Most policies will require thorough referencing of tenants in order to minimise the risk of having to pay out; but this is good landlord practice anyway.

As Tony points out, however, policy providers often want referencing done a certain way.

"In circumstances where the insurance company's own referencing service has to be employed, they often also insist on landlords using the policy provider's specific tenant application form - and for the applicant to be approved before a tenancy is granted.

So, check the conditions carefully with each policy provider, before signing a tenancy agreement."

A policy can sometimes seem like an unnecessary expense, especially when a tenancy is running smoothly, but landlords should note that its costs, along with referencing expenses, can be set against rental income for tax purposes.

There is no doubt that landlords' heightened fear of non-performing tenants is increasingly seeing them running for cover - insurance cover.

Richard Lamberth, an MD with insurers Towergate (www.towergatepartnership.co.uk) said: "The letting market is very buoyant with many people putting off property purchase for the time being.

"At the same time the threat of job insecurity is making landlords nervous and many more are reaching for the protection of rental guarantee insurance to kick in if a tenant defaults on rent. We have noticed a 15% increase in take up since October 2008 and this continues to be unabated."

Towergate, for example, offers a policy that covers the landlord if a tenant stops paying rent for any reason, or if they simply disappear. Cover can be based on a six or a 12 month contract.

Tony Booth again: "Very few buy-to-let annual yield formulas include such protection as part of the profitability calculation, but my own assessment of 'worthiness' when choosing a new property to invest in always includes the rent guarantee expense.

"'For me, it is quite simply a crucial part of running my property letting business - and considered on a par with an allowance for one month's void per annum or setting a sum aside for general maintenance.

"'Perhaps more importantly, it means I sleep well at night."

And for those curious, here's the NLA's list of landlords' top five concerns based on helpline calls:

1. What procedure do I follow, when my tenant has stopped paying rent?
2. What is an Energy Performance Certificate?
3. I instructed a letting agent on a 'finder's fee' only, my tenant has been there for six months, my agent now wants a fee to just do the renewal paperwork.
4. How are disputes within tenancy deposit protection handled?
5. Do I need a licence for my HMO (House in Multiple Occupation)?