The RSPCA and Guide Dogs for the Blind Association have more than £230m in the bank between them, BBC Radio 4's Today programme discovered.

Visually impaired Mike Mitchinson on Guide Dogs for the Blind: Far too many staff

Guide Dogs for the Blind's reserves gather £7m a year in interest, nearly a fifth of its annual income, or a third of its staffing costs.

Its reserves have also grown strongly over the past few years, thanks to the strong performance of the stock market.

But few charities will admit to having too much money and most cite the unpredictability of future income to justify their huge reserves.

Guide Dogs for the Blind spends £30,000 to train and feed and look after each guide dog throughout its working life and has a running yearly deficit of nearly £10m.

The charity's chief executive, Geraldine Peacock, is currently reviewing all the charity's activities, investments included.

'Can exist without income'

She said: "The investments that we had made over the years with legacy income performed very well on the stock market and our reserves have grown greatly in the last five years.

"So for the last 15 months we have been taking a long hard look at the organisation and its future to see what we could do with this improved income to improve the range of services that we could offer."

Today asked BDO Stoy Hayward, one of the UK's biggest accountants, to look over the books of a number of large charities including Guide Dogs for the Blind and the RNLI.

Kate Kirkland of the company's charities unit, said: "They have enough money to exist for several years without a penny of income, but fundraising is complex.

"For charities, you cannot switch your fundraising off and on."

'Lack of transparency'

The RNLI has more than £250m invested and assets worth another £150m.

Ray Kipling, the charity's deputy director, said: "It will cost us, we estimate, £80m to run the lifeboat service next year.

"We can't stop the boats going out if we don't have enough money."

Mr Kipling said 20 years ago "we were down to virtually no reserves and we were making plans to close lifeboat stations. That is not a situation we can contemplate now".

But charity finances suffer from a chronic lack of transparency, says Guy Stafford, co-author of a report on charities for the conservative Bow Group, which seeks to influence Conservative Party thinking.

He said: "A company has a clearly defined objective which is to raise money or make profits.

"The problem is that it is almost impossible to know what charities do with the money that is donated to them."