Britain has voted to leave the European Union in an historic referendum which has thrown Westminster politics into disarray and sent the pound tumbling on the world markets.

Wirral voted by a small majority at 51.6% to Remain while neighbouring Liverpool showed its pro-European credentials with 58% opting to stay in the union.

St Helens was the most Eurosceptic area in Merseyside with 58% voting to leave, followed by Halton where 57.4% opted for Brexit.

HOW BRITAIN VOTED -

OUT: 17,410,742

IN: 16,141,241

TURNOUT: 72.2%

Ukip leader Nigel Farage declared that June 23 should "go down in history as our independence day", while Vote Leave's chair, the Labour MP Gisela Stuart, said it was "our opportunity to take back control of a whole area of democratic decisions".

Sterling suffered one of its biggest plunges in the overnight markets, hitting lows last seen in 1985 and losing more than 10% against the US dollar, as traders responded with panic to the prospect of the UK quitting the European Union after 43 years.

With Prime Minister David Cameron expected to address the nation from Downing Street before financial markets opened at 8am, Labour said he should "seriously consider his position", while Mr Farage said he should resign immediately after voters rejected his passionately-expressed advice to stay in the EU.

Bank of England Governor Mark Carney is expected to make a statement after Mr Cameron.

As polling stations closed at 10pm on Thursday with polls still predicting a Remain victory, 84 pro-Leave Tories - including Boris Johnson and Michael Gove - handed a letter to Mr Cameron urging him to stay on as leader whatever the result of the referendum.

But as Leave built an increasingly unassailable lead as the night wore on, with victories in the Tory English shires, Labour strongholds in the north, Wales and Midlands, others in his party raised questions about Mr Cameron's future.

Long-standing Eurosceptic John Redwood suggested Tories should wait to see if Mr Cameron was willing to "implement the public will" after a Leave vote.

Mr Redwood said the PM should bring in talent from the Leave side to build "a new government to bind the country together". And Conservative backbencher Jacob Rees-Mogg said a general election in the autumn was "not impossible".

Influential backbencher David Davis said the Prime Minister could stay on for a "couple of years" but should put someone else in charge of negotiations on a new relationship with the EU.

Shadow chancellor John McDonnell said the Bank of England may have to intervene to shore up the currency. Mr Cameron would now be "a hostage" to his pro-Brexit MPs, who will make sure they seize "key positions", he said, warning that "ordinary people must not pay the price" of the Leave victory.

Speaking at the Electoral Commission's main counting centre in Manchester, Ms Stuart said that all political leaders should "reflect on whether they have accurately gauged the people's desire to govern themselves".

The German-born MP said a calm cross-party effort was now needed to implement voters' decision "in the best long-term interests of this country". And she broke into her native tongue to assure other EU nations that Britain would remain an "open, welcoming" country which would continue to co-operate with its former partners.

Leaders of the European Commission, Council and Parliament were due to give their initial response at a press conference in Brussels, amid speculation that a leaders' summit scheduled for Tuesday may be brought forward to deal with the decision.

Senior Labour backbencher and former Europe minister Keith Vaz said the EU should call an emergency summit to deal with the aftermath of the vote, which he described as "a crushing, crushing decision ... a terrible day for Britain and a terrible day for Europe".