Britain's terminally ill should receive a new cash rebate brought in by energy companies for "vulnerable" customers because many cannot afford their fuel bills, ministers are being urged.  Leading health charities and doctors want all those dying of conditions such as cancer, heart problems, aids and motor neurone disease to qualify automatically for a ? 130 annual discount. They often have high gas and electricity bills because they are forced to stay at home during treatment, and most struggle to find the money because they are jobless.  Macmillan Cancer Support, the British Heart Foundation and representatives of people with other medical conditions have signed a joint statement which they hope will persuade the energy and climate change secretary, Chris Huhne, to make sure the terminally ill get the rebate.  Britain's six biggest energy suppliers will start giving annual rebates of ? 130 from april after the government told them to do more to help people in fuel poverty. The three-year scheme will cost an initial ? 250m.  Under the new Warm Home Discount a core group of vulnerable energy users, including older people receiving pension credits, will automatically receive the rebate. a second broader group, including families with young children, the disabled and those with a long-term condition, will have to apply for it.  In their joint statement the charities warn that people dying of cancer or other terminal conditions will lose out unless they are seen as core recipients. "More often than not the higher bills come at a time their household income drops because they are unable to work. Terminally ill people must be included