"After another week of turmoil in mortgage markets, novice landlords now face huge difficulties securing a loan, and thousands of existing landlords coming to the end of fixed-rate deals will find it very hard and very expensive to switch mortgage providers if they have not built up at least 75 percent equity in their buy-to-let property," Katie Tucker of the real estate broker John Charcol told The Times of London.

HBOS, a group that is the largest mortgage lender in the country, has increased its rates three times in three weeks, the Times said.

Cheltenham & Gloucester, the fourth largest lender, hiked some rates three times in two weeks.

"It's the amateur investors who are feeling the pinch," said Chris Wood of the National Association of Estate Agents. "With lenders worried about falling house prices, prospective borrowers without a substantial deposit will find it very tough to get a buy-to-let loan."