NICOLA Sturgeon could be invited to attend the UK Cabinet, if the Liberal Democrats won power, in a move aimed at giving the Scottish Government “a greater say” on UK-wide policy-making, Ed Davey, the deputy leader, has suggested,

The prospect was raised as the Lib Dems unveiled their election manifesto in London, which places scrapping Brexit at the heart of the party’s election campaign.

The Lib Dems calculate that Britain would benefit from a £50 billion “Remain bonus” over the five years of the next Parliament, thanks to higher growth from staying in the EU. The extra cash would be ploughed into improving public services and creating a fairer and more equal society.

The dividend of staying in the EU reaches more than £14bn by the year 2024/5 with Scotland receiving a knock-on windfall of £3.4bn in that year.

On constitutional matters, the party restates its opposition to Scottish independence and holding another referendum on the subject.

Ensuring that Scotland has a strong voice in the UK, it proposes extending the involvement of Edinburgh in the development of UK-wide policies.

Asked, at a briefing for Westminster-based journalists, if this could mean the First Minister attending a Swinson Cabinet on certain topics, Sir Ed replied: “The idea of the First Minister attending Cabinet makes perfect sense to me but, because we believe in co-operating with different parts of the UK, we want to develop these ideas in consultation…We want to ensure the different countries of the UK feel they have a greater say; that’s our ambition.”

He stressed he was deeply worried about the UK’s future under the policies of Labour and the Conservatives.

“The unity of the UK is on the ballot paper,” he declared, “and we are the only party that wants to keep the UK together by our policies and not just by Johnson rhetoric.”

The deputy leader stressed how the Joint Ministerial Committees, the intergovernmental forums, would be beefed up and increased in frequency. “We would take them seriously,” added Sir Ed.

The party’s raft of proposals also includes:

*spending up to £10bn extra a year on schools south of the border, allowing them to employ 20,000 additional teachers and to reduce class sizes - this alone would provide the Scottish Government with a £1bn boost;

*slapping 1p on income tax in England and Wales to help improve mental health and social care with a plan to inject £11bn over the five years of the next Parliament;

*freezing rail fares for five years, increasing taxation on frequent international flyers and opposing Heathrow expansion;

*by 2030, instigating an emergency programme to insulate all homes, investing in green power to mean at least 80 per cent of electricity is generated by renewables and ensuring all new cars are electric;

*35 hours’ free childcare a week for all two to four-year-olds south of the border;

*maintaining a minimum nuclear deterrent with a “medium-readiness responsive posture,” which would see the abandoning of the current continuous at sea deterrence and

*legalising cannabis with the taxed drug sold in regulated shops to people over 18, bringing in almost £1.5bn a year to the Exchequer by 2024/5.

Amid bright spotlights, beat music and a garish yellow-orange backdrop Jo Swinson appeared on stage on Wednesday evening to launch her party’s manifesto in a black-walled bar in Camden Market; complete with a bare wooden floor and surfboards nailed to the ceiling.

The venue was filled with punters wearing yellow rosettes, yellow scarves, yellow shirts and yellow dresses and holding pint glasses.

Eventually after being trailed as the “real alternative” and the “voice of Remain,” the party leader bounded onto the stage to denounce the “two tired old parties” led by people who would simply rehash the past “whether the 1970s or the 1870s”.

An animated Ms Swinson rattled off a series of policies contained in the party’s manifesto booklet, promising to save the Union as well as providing more spending on schools, child care, mental health and climate change; all funded from the £50 billion “Remain bonus”.

The party leader insisted if people wanted to stop Boris Johnson and his “cabal of hardline Brexiteers,” then they had to vote for the Lib Dems.

However, the Scot seemed to have given up on the ambition to enter Downing St by increasing her number of MPs from 20 to 320 as she insisted the Lib Dems were now the “only party that can win a significant number of seats from the Conservatives and deprive them a majority”.

Earlier on a campaign visit to Cambridge, Ms Swinson argued the party's manifesto showed it was not a "one-trick" anti-Brexit party. But she admitted the Lib Dems were suffering a "squeeze" in the polls.

“But,” the party leader added, “at this point in the 2017 election the polls weren't a very good indicator to what actually happened in the final outcome."

Meanwhile, Paul Johnson of the respected economic IFS think-tank said the Lib Dems had followed the other parties in increasing investment spending; a little bit more than the Tories but a lot less than Labour.

But he noted: “If it were to become clear not only that we were going to Remain but that that was a settled state for the long term, we could expect some additional growth and with it additional tax revenue. Their estimate is within the range of plausible estimates for the extent of that additional revenue.”