Nationwide, the UK’s biggest building society, has said that from today it is no longer accepting transfers of cash Individual Savings Accounts (Isas) from other savings groups.

The move follows complaints by savers that they have had to wait months to transfer cash Isas to Nationwide from other banks and building societies.

Nationwide accepts its transfer process has grown more sluggish and blames the delays on the sheer weight of money being switched from other financial groups.

A spokesman said: “In the past few months we have seen a huge increase in the number of Isa transfers we are receiving. They are running at tens of thousands each month - five times the level of twelve months ago - and as a result we have not been able to maintain our normal level of service. So we have decided temporarily to suspend transfers of Isas from other providers while we take stock of the situation.”

He could not forecast when transfers would be resumed but expected it would be within weeks rather than months.

Savings experts say the flood of money into Nationwide’s coffers is explained by two things: the very competitive rate of 6.15 per cent it is paying on its one, two and three year Isa bonds and a flight to safety by savers worried by the problems at Northern Rock and other banks.

But the popularity of Nationwide’s products has backfired as savers have experienced frustration and delays in trying to transfer money from other less attractive Isa providers. Instead of switches being completed in the regulation 30 days they have sometimes taken more than two months.

James Dell, a Times reader, said: “I filled in the transfer forms at my local Nationwide branch but the transfer was not made after four weeks. About three weeks later my ‘old’ Isa account was closed and a letter sent saying funds were being transferred but after a further two weeks nothing had happened. I rang Nationwide who said it could take a further six to eight weeks to complete the transfer. I am too fed up with Nationwide to bother and am moving my money to another bank.”

Nationwide said all cash Isa transfers started before today will be completed and its range of cash Isa products remains available both to new customers who have not used this year’s allowance and to existing Isa customers wishing to switch between different Nationwide accounts. Stocks and shares Isas are not affected by the latest move and Nationwide is still accepting transfers in.

Nationwide has a total of four million cash Isas and is the UK’s second biggest savings provider.

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