Previously, Coutts clients had to hold £500,000+ in investable assets before taking out a mortgage loan with the lender.

Coutts said that the criteria change is a “rough guideline” and that it is “not set in stone.”

“If we felt that a client’s case looked appropriate without the £1m in place then we would consider doing business with them,” said a spokesman.

Coutts added that the new guidelines only “slightly alter” the previous criteria.

The lender said that all mortgage clients will have to be Coutts account holders just as before and the loan application process will remain the same.

Ian Gray, mortgage manager at Largemortgageloans.com said: “There are other private banks and high street lenders that lend without investable assets; this would be an option for clients who do not fit Coutts’ criteria.

“The drawback to this is that many of the other private banks are ultra conservative on lending so clients may not be able to get the higher loan to value products that Coutts offers”

Mortgage clients who bank with other lenders would also miss out on some of Coutts’ more unique product features including a pure offset mortgage and deals longer than a five-year term, added Gray. He said unlike many other private banks, Coutts also pays its brokers proc fees.

“There aren’t many brokers who do business in the high net worth mortgage market, but for those who do, they will have to start negotiating a higher fee with their clients,” added Gray.