Britain's long-term fiscal prospects showed a gap of 100 billion pounds (about 155 billion U.S. dollars) developing between income and expenditure, the British government's independent economic forecaster the Office of Budget Responsibility (OBR) said Friday.

The OBR's Fiscal Sustainability Report said that Britain's public finances are likely to come under pressure over the longer term, 2020-2060, primarily as a result of an ageing population.

The gap is roughly similar in size to the amount already being cut from government budgets over the next five years to restore balance to the budget after expenditure in the wake of the global financial crisis.

The report said the government would have to spend more as a share of national income on age-related items such as pensions and health care, but the same demographic trends would leave revenues stable as a share of national income and not rising to match the higher demand.

Without revenue increases, like tax, or spending cuts, this would increase public debt. The OBR report commented that it was likely that this "would lead to lower long-term economic growth and higher interest rates, exacerbating the fiscal problem."

Paul Johnson, director of the Institute of Fiscal Studies (IFS), told Xinhua, "One option is to raise taxes; they can see it is an ageing population and do not want to reduce services. If they decide to do that we would argue they need a more sensibly designed and efficient tax system."

This big increase in spending is in pensions and health, Johnson said longer term attempts to tackle the looming deficit had begun with the extension of the retirement age to 67 by 2026 but other measures would be needed.

Johnson said the British governments of the future needed to consider the merits of cuts to state social security payments and housing subsidies as well as reform to the tax system.

Britain's long-term financing problems were far from unique among developed world economies, said Johnson, "There are similar problems across the world. In many countries there is an ageing population and future increased costs."