A PENSIONER has told of her shock after her electricty supplier demanded she increase her monthly payments by a staggering 600 per cent.

Nan Cameron, 81, was sent a letter by Scottish Gas telling her they were set to increase her direct debit payments from £120 to £733 per month.

The demand came as Mrs Cameron, a widow who is under medication for an irregular heartbeat, battled with the utility giants over claims on unpaid bills.

Mrs Cameron's wrangles with Scottish gas - whose parent group Centrica announced rises of 35 per cent in house hold fuel bills this month - began earlier this year.

She was sent a bill for £6151.11 in May which Scottish Gas said was mostly made up of underpayments on her account dating back to July 2006.

Shocked Mrs Cameron of Strathaven, Lanarkshire, complained to the company.

And with the help of her neighbour Alastair Murdoch, they succeeded in having the claim reduced to £691.08p after Scottish Gas admitted a billing error.

They conceded they had mistakenly 'twisted' her billing, meaning the wrong tariffs were used for calculating bills.

However Mrs Cameron then received a second demand in July telling her she was in debit for £5025.61.

She again challenged Scottish Gas who admitted their error for a second time.

But a disbelieving Mrs Cameron was then sent a letter dated July 17 telling her her monthly payments were to rise to £733 a month - a jump of 611 per cent.

The letter read: "No one likes getting bigger bills than they expected. So to make sure there are no surprises when British Gas bills arrive, we regularly review our customers payment plans.

"Twice a year we look at the cost of the electricty you've been using as well as what you're likely to spend in the coming year."

Last night Mrs Cameron, a grandmother of six, said: "Every time a letter came in I was shocked further. I wasn't worried because I knew it wan't true. It was ridiculous.

"When the bills came in I told them it was their fault and not mine. Their ineffiency appalled me I and told them as much.

"I used to work in a bank and always check my bills and accounts so I am sure of what I owe and don't owe and I knew I didn't owe Scottish Gas thousands of pounds.

"My concern would be for some other person out there who may not be a fiesty character like myself and who may be bullied into accepting what letters companies of this size send.

"They should take care to double check and know what they are signing.

"When I called Scottish Gas the boy on the phone tried to dismiss this demand for £733 a month as a typist error.

"But I said this has been signed and told him it was unacceptable."

Mrs Cameron has now told Scottish Gas she is switching suppliers.

Yesterday a spokesman for Help the Aged said: "It is very important that simple things like billing is done properly as old people have enough to worry about at this time."

Last night a spokeswoman for Scottish Gas said: "Scottish Gas have apologised to Mrs Cameron for the problems she has experienced with her bills and we are working with her to find a resolution which we hope to reach shortly."