Any snap general election must be conducted under a new proportional voting system to ensure a representative parliament after the EU referendum, Nigel Farage has said.

The Ukip leader is one of a number of signatories of an open letter arguing that the mandate of the current government does not extend to negotiating Britain’s exit from the European Union.

The letter, organised by campaign group Make Vote Matter, is also signed by Tim Farron of the Liberal Democrats, Natalie Bennett and Caroline Lucas of the Green Party, and Plaid Cymru Westminster leader Hywel Williams.

They say that a newly elected parliament is required to make “fundamental choices” in the aftermath of the referendum result and that it should be constituted according to the votes cast.

Mr Farage told The Independent that it was not sensible for Ukip to be artifically excluded from parliament when it was the only party in Great Britain to actively support the winning side of the referendum.

“Ukip have supported a representative electoral system for many years now. The result of the referendum merely goes to highlight the disconnect between the political parties and the public,” he said.

“Ukip was the only party on mainland Britain to support the winning Leave campaign. The others, nestled in Westminster, Holyrood and Cardiff, campaigned against the people.

“With a sensible system that actually reflected the wishes of the public, maybe the chaos we are now witnessing within the relict establishment may not have been so devastating.”

The letter notes that during the campaign “senior Conservatives – from David Cameron, to Liam Fox and Iain Duncan Smith – were filled with enthusiasm that this was a democratic process in which every vote matters”.

It continues: “Yet under our antiquated First Past the Post voting system, votes are anything but equal.”

Liberal Democrat leader Tim Farron is another signatory (Getty Images)

At the last general election Ukip won just one of 650 seats from nearly 13 per cent of the vote. Conversely, the Scottish National Party won 56 MPs on 4.7 per cent of UK vote.

The Conservatives meanwhile won a majority of more than 50 per cent of seats with support from just 36.8 per cent of electors.

Most other countries in Europe use proportional voting systems that result in seats accurately reflecting votes cast. The Scottish Parliament, Welsh Assembly, Northern Ireland Assembly, and London Assembly also use systems that achieve this goal.

Green MP Caroline Lucas also supports the letter (PA)

The news comes as Mr Farage strongly hinted that Ukip’s only MP Douglas Carswell could be kicked out of the party on Monday.

He told LBC radio that Mr Carswell “doesn’t agree with anything the party stands for” and said it would be up to the NEC to decide “on Monday”.

Mr Carswell, who is on UKIP’s NEC, said he had received the agenda for Monday’s meeting and had not noted any move against him.

“Normally in political parties if you want to kick someone out there tends to be a procedure. Up until five minutes ago [when alerted to Mr Farage’s comments by the media] I was not aware of anything,” he told The Independent.

He added that he was not aware of any disciplinary action against him, and said he would enjoy a restful weekend celebrating Britain’s vote for Brexit.

Douglas Carswell, Ukip's only Member of Parliament at Westminster (PA)

Reform of the voting system has been slow at Westminster due to longstanding opposition from the two major parties who benefit most from the current system.

There are signs that reform could be on the way. In May, shadow chancellor John McDonnell said Labour should back proportional representation – the highest office holder to say as much publicly in decades.

The letter, which accompanies a petition also signed by 14,000 other people, reads: “Following the EU Referendum the most important questions still have to be answered, including decisions about trade and immigration, foreign policy and sovereignty.

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“The 2015 general election manifestos did not include plans for a Britain out of Europe and the people have endorsed no particular exit plan.

“The fundamental choices we make in the next two years will shape the United Kingdom for decades to come. For these choices to be democratically legitimate, we need a parliament elected under a system of Proportional Representation; one in which all votes matter equally.

“We, the undersigned, call for the Tory leadership to live up to the democratic values they endorsed during the referendum campaign by acknowledging this.”

Klina Jordan, co-facilitator at Make Votes Matter, said: “There is a growing realisation amongst ‘leavers’, ‘remainers’ and abstainers that Parliament does not accurately reflect the voters.

“87% of OECD nations use proportional electoral systems – and proportional systems correlate globally with higher voter turnouts, better gender representation, greater economic equality, faster action to tackle long-term risks like climate change, and more.

“The time to get rid of our antiquated and unfair electoral system has come.”

Hopes of an early election appear to have faded as the frontrunners in the Conservative leadership race all say they do not want to hold one.