An increasing proportion of Britain's landlords are remortgaging in an attempt to raise the capital necessary to expand their portfolios, according to figures released by Mortgages for Business.

The statistics show that 80 per cent of investors and buy-to-let mortgage holders who own houses in multiple occupation had refinanced these assets in the final quarter of 2012 - up from 55 per cent in Q4 of 2011.

And with a small increase in the proportion of landlords who own multi-unit freehold blocks taking the same approach - up from 76 per cent to 78 per cent in the same period - it appears that there is a strong appetite among investors to make further inroads in the lettings game.

David Whittaker, managing director of Mortgages for Business, said: "Gross yields on buy-to-let property are particularly attractive at the moment thanks to the mess which the first-time buyer market finds itself in.

"Property prices are flat and tenant demand is stratospherically high, which is why more landlords are refinancing and manoeuvring themselves into a position to add to their portfolios."

With demand among tenants continuing to have an impact on rental prices and the shortage of supply providing landlords with the security of knowing that it is likely competition for their properties will be high, it is unsurprising that so many are looking to widen their portfolios.

And as a number of investors have claimed that it is difficult to find the finances to do so in a tough economic climate, it seems that remortgaging is becoming a popular way for landlords to raise the capital they need to acquire new assets.

But despite the boom in the buy-to-let sector, it's vital that investors remember the importance of protecting their financial interests as efficiently as they can - a factor which makes landlord insurance policies vital to their long-term profits.