LONDON, June 27 (Xinhua) -- The financial cost of Britain leaving the European Union remains uncertain, the House of Commons Public Accounts Committee said in a report Wednesday.

The committee, made up of MPs, also said it could be years before any so-called Brexit dividend materialises.

British Prime Minister Theresa May said last week that extra funding for the cash-strapped National Health Service (NHS) will be part funded by money Britain saves by not paying its dividend to Brussels for its EU membership.

The committee report says it has found any "EU dividend" will be hard to calculate and, if it materialises, is some years away

The report said: "Overseeing the UK's withdrawal from the European Union is one of the biggest challenges that has faced any government.

The cost to the UK of leaving remains uncertain because it depends on future events, such as the UK's economic growth."

It added there is a risk that the amount Britain actually pays to Brussels will fall outside the narrow range estimated by the British Treasury of 35 billion to 39 billion pounds (46 to 52 billion U.S. dollars).

"There is much talk of an EU dividend but our work has highlighted a number of as yet uncertain costs. Any dividend will be hard to calculate and, if it materialises, is some years away," said the report.

MP Meg Hillier, who chairs the committee, said: "The true cost of Brexit is a matter of outstanding public interest. Government must provide parliament and the public with clear and unambiguous information.

"The government's narrow estimate of the so-called divorce bill does not meet this description. It omits at least 10 billion pounds of anticipated costs associated with EU withdrawal and remains subject to many uncertainties.

"The UK's contribution to the EU's outstanding commitments and liabilities after 2020 is unknown. The estimate also excludes costs that may arise from parts of the withdrawal agreement still to be negotiated."

Hillier said British payments to cover EU pension and benefit costs could run for decades."

She added: "There are other potentially significant ongoing costs likely to arise from post-Brexit restructuring, for example, new trade and customs arrangements, replacement institutions and the costs of participating in EU programs as a non-member state."

Hillier said it is critical parliament and British taxpayers are kept informed as agreements are reached and new information becomes available.

"A parliamentary vote on EU withdrawal will only be truly meaningful if this information is disclosed in a timely fashion. Government must explain how it will approach this task and waste no time in getting on with it," said Hillier.