Stopping Brexit will deliver a £50bn “Remain bonus” for public services over the next five years, Liberal Democrat leader Jo Swinson will say later.
In a speech at the party’s campaign launch, she will claim the extra £10bn a year will be due to the UK having a larger economy by staying in the EU.
Also on Tuesday, Jeremy Corbyn will make a speech accusing the PM of trying to “hijack Brexit to sell out our NHS”.
And he will pledge to “get Brexit sorted” within six months if he is PM.
Meanwhile, in a letter on Monday night, Boris Johnson called on Labour leader Mr Corbyn to “come clean” on his Brexit proposals, claiming Labour’s current position was “to go back to square one”.
The political parties are ramping up their election campaigning, ahead of the official start to the five-week campaign period at just after midnight on Wednesday.
The UK will go to the polls on 12 December.
Launching her party’s anti-Brexit election campaign on Tuesday, Ms Swinson is expected to say: “The Liberal Democrats are the only party standing up to stop Brexit and build a brighter future for the UK.
“Brexit has taken far longer and cost far more than anyone said it would.
“But any form of Brexit will damage our jobs, our economy and our public services, starving them of vital cash as the economy struggles along.”
The party said the £50bn figure – the amount that it has calculated will be saved over the next five years by staying in the EU – is based on the UK economy being 1.9% larger in 2024-25.
It reflects the extra tax income over the next five years and is based on a 0.4% average annual boost to GDP if the UK stays in the EU.
Deputy leader Sir Ed Davey told BBC Radio 4’s Today programme that the Lib Dems “actually think these are quite cautious figures”, adding that all the independent forecasters “were clear that there will be a big boost if we stay”.
Paul Johnson, from the independent Institute for Fiscal Studies, said it was a reasonable calculation in line with their own forecasts, adding: “We could expect the economy to be bigger if we were to remain and this assumes a relatively modest effect if anything, although obviously subject to a huge amount of uncertainty”.
Meanwhile, Mr Corbyn will again seek to portray a post-Brexit trade deal with the US as a threat to the NHS.
In a speech in Harlow in Essex, the Labour leader will say government plans for a post-Brexit trade deal with the US could see an extra £500m a week spent on buying medicines.
“We now know that US and UK officials have been discussing drug pricing in secret and the US government is demanding “full market access for US products,” he will say.
“Senior NHS managers have said that would mean “higher prices for medicines” which will “pass on costs to both patients and the NHS.”
The Lib Dem and Labour figures fact-checked
Labour’s £500m figure is based on a report written by three academics – one of whom appeared in a recent Channel 4 Dispatches programme on the price of medicines. The report says it can ‘crudely estimate’ what would happen if – after a future trade deal with the United States – the prices of all medicines used in the NHS were the same as the prices of those medicines in the US.
For those who want to keep NHS prices down – it is a theoretical worst case scenario.
The current overall cost of NHS medicines in England is about £18 bn per year, and (according to the OECD) expenditure on medicines per person in the US is roughly 2.5 times higher than in the UK. That produces a notional figure of £45bn per year for England if all prices were the same, and a difference of £27bn – just over £500m a week.
In practice it’s highly unlikely that all prices would end up being exactly the same – but there’s no question that US pharmaceutical companies will lobby aggressively for greater access to the NHS, and the ability to set higher prices.
If the government refuses to discuss the price of medicines at all in trade talks, American negotiators will refuse to discuss other kinds of market access that the UK would be keen to have in the US.
As for the Liberal Democrats’ calculation – of a £50bn ‘Remain bonus’ over five years – the vast majority of forecasts do expect the economy would be bigger if the UK were to stay in the EU.
The independent Institute for Fiscal Studies says this forecast is reasonable. But it can’t be predicted with any certainty, and it’s not a hugely significant amount in terms of overall government expenditure.
Mr Corbyn will also claim Boris Johnson’s Brexit deal will lead to “Thatcherism on steroids,” with a “race to the bottom” on workers’ rights and product standards.
“Given the chance, they’ll slash food standards to US levels where ‘acceptable levels’ of rat hairs in paprika and maggots in orange juice are allowed,” he will claim.
He will say a Labour government would negotiate a “sensible” Brexit within three months of taking office, which would then be put to a referendum alongside the option of remaining in the EU.
Labour has said, if elected, it would negotiate a withdrawal agreement for the UK to remain in an EU customs union, and retain a “close” single market relationship.
The party has not said whether it would back Leave or Remain if another referendum took place, but Mr Corbyn will promise to “immediately carry out” the decision made.
‘More dither and delay’
Meanwhile, in a letter to the Labour leader, Boris Johnson accused Mr Corbyn of refusing to say what sort of deal he would seek with the EU.
The prime minister added that Mr Corbyn’s plan to renegotiate a new Brexit deal would take “months and possibly years to do”.
“Under your proposals, 2020 will be lost to more dither and delay over Brexit,” he wrote.
“For months you have refused to say what sort of ‘deal’ you want with the EU,” he added.
“Now the time has come for you to come clean, and explain what your plan really is”.
SNP leader Nicola Sturgeon will also be focusing on the issue of Brexit, as she campaigns alongside the party’s candidate in Midlothian on Tuesday.
Speaking ahead of the visit, Ms Sturgeon said it was not a “done deal” that the UK will leave the EU.
“We’re already sick of Brexit – we don’t want it to go on another 10 years or more,” she said.
“So Scotland must not face a lost decade of Brexit chaos that we didn’t vote for.
“A vote for the SNP is a vote to escape from Brexit and for Scotland’s right to choose our own future.”