Borrowers are increasingly keeping their existing home to rent out while buying a new main residence, it is claimed.

Independent mortgage advisers John Charcol says the let to buy sector is growing in popularity as more people wake up and realise the benefits.

The firm points out that it helps manage the problems of chains, enables borrowers to sell a property at a time that suits them, and is increasingly used as an opportunity to boost retirement income.

John Charcol witnessed a 40% increase in the proportion of its clients using let to buy mortgages last year - a trend that is continuing into 2013.

Ray Boulger, senior technical manager at the mortgage advisers, described let to buy mortgages as a "great option" for many borrowers.

He said it is a "genuinely compelling solution" for people looking to improve their buying power, limit their stress, take control of when you sell and/or boost their retirement income.

"Our experience is that the popularity of let to buy has been progressively increasing since the nadir of the buy to let sector in 2009,"added Mr Boulger.

"I think this is primarily attributable to home owners' renewed confidence in the housing market, coupled with the increasing demand for rental property."

While the let to buy market grows in popularity, the firm believes that the buy to let market has been the driver of the recent modest increase in gross mortgage lending and from 2010 has increased steadily, culminating in gross lending of £16.4 billion in 2012, representing 11.5% of the total market.

"Buy to let has been far and away the strongest sector of the mortgage market since the whole market reached its nadir for gross lending at £135.3 billion in 2010," continued Mr Boulger.

"When gross mortgage lending peaked at £362 billion in 2007, buy to let accounted for 12.3% of lending. However, it then fell away even more rapidly than mainstream lending and in 2009 was just 5.9% of the market."

Although let to buy only accounts for a modest part of the increase in gross mortgage lending, some home owners obtain permission to let from their mortgage lender. This means they retain their existing residential mortgage, rather than remortgage to a buy to let deal.