Published: 2:02 PM July 10, 2018 Updated: 8:41 AM September 18, 2020

Brexit day would be one of "mourning" if it happens, Sir Vince Cable claimed, as he warned no deal would lead to "anarchy" for UK trade.

The Liberal Democrat leader told MPs it would be difficult to see the positive story of Brexit to help the country "turn over a new leaf" as many regard it as a "disastrous error" while lifelong Eurosceptics fear the government is betraying them.

He also said the "completely hollow" World Trade Organisation was losing its authority due to the actions of US president Donald Trump, meaning that if the UK were to fall back on the body's trading rules then it would be "effectively falling back on anarchy".

Sir Vince's warnings came as the Lib Dems made a fresh Commons push for a People's Vote to allow the public to have a say on the deal negotiated with the EU.

Tory former minister Marcus Jones claimed the Lib Dems did "not trust the people" over Brexit while Cabinet Office minister Chloe Smith said just 7.4% of voters backed the party and its second referendum stance at last year's general election.

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Shadow Brexit minister Jenny Chapman said Labour "doesn't want an exit from Brexit" as she rejected the non-binding motion, which also suggests the possibility of creating a government of national unity.

Leading the Opposition Day Debate, former business secretary Sir Vince said Brexiteers had "poisoned their own well" via their resignation comments, in a nod to David Davis and Boris Johnson.

He said: "It's extraordinary to which the extent the phrase 'betrayal' is entering the narrative.

"We risk getting to a point in a few months' time if Brexit happens - and I think it's an if rather than a when - in which one side here, the many people who regard Brexit as a disastrous error, will be pointing out the many problems that arise from it, and those who have devoted their lives to fight for Brexit will be arguing it is a disaster because it is a betrayal.

"If Brexit day ever happens, it will be a day of mourning and it is very difficult to see where the positive story is going to come from to help the country turn over a new leaf."

Sir Vince later said there appeared to be an "implicit acknowledgement" from the government that "crashing out" of the EU is "less and less plausible" due to the changing international environment created by Mr Trump.

He went on: "The United States is not willing to abide by its rulings, it's not willing to staff its judicial panels, as an organisation it's completely hollow.

"Were we to fall back on World Trade Organisation rules, we're effectively falling back on anarchy."

Replying for the government, Ms Smith said: "We are respecting the result of the referendum and we are delivering Brexit - there will be no second referendum."

She added: "In last year's general election, more than 80% of voters supported Conservative and Labour together - both parties' manifestos committed to respecting the result of the referendum.

"Now let's not forget just how many voters supported the Liberal Democrats' position, whose manifesto called for that second referendum - it was 7.4%."

For Labour, Ms Chapman described the motion as a "greatest hits" of Lib Dem policies over the last decade.

Setting out Labour's position, Ms Chapman said: "We don't want an exit from Brexit, we respect the outcome of the referendum."

On the proposal to form a "government of national unity", Ms Chapman said: "Of course the Labour Party is open to working across the House to find a consensus and shape the Brexit process to protect jobs and the economy.

"But this motion calls instead for a government of national unity, in other words a coalition, and I know this is the Lib Dems' answer to any moment of political crisis - but we do not agree, the proposal in the motion poses more questions than it answers."