Liberal Democrat leader Jo Swinson revealed she smoked cannabis while at university, saying: 'I enjoyed it.'

The Scottish MP, 39, said she would not be one of the hypocritical politicians who dodged the question or pretended any dalliances with drugs were regretted.

She told Newsnight: 'I'm not going to be one of those people who says "I tried it once and I didn't really inhale".

'Yes, I enjoyed it. And it wasn't unusual… lots of people do it and we should enable them to do it more safely.'

The interview came hours after she unveiled her party's election manifesto, which contained plans to legalise cannabis.

Stoner student: Jo Swinson, the current Lib Dem leader, pictured left in 2000 with, among others, the party's former MP Lembit Opik, front centre

Miss Swinson tried to stop her party's sliding poll ratings as she unveiled the Liberal Democrats' general election manifesto with key pledges to stop Brexit alongside the overhauled drug policy.

Arguably the party's most eye-catching policy apart from Brexit, they pledged to legalise cannabis and to introduce a licencing system which would allow the drug to be sold over the counter to over-18s.

The party said in its manifesto that introducing a 'legal, regulated market for cannabis' would 'help to break the grip' of criminal gangs.

Miss Swinson told Newsnight (pictured) that smoking cannabis should be legal for over-18s

The document said: 'We will introduce limits on the potency levels and permit cannabis to be sold through licensed outlets to adults over the age of 18.'

The Lib Dems claim that the 'prohibitionist attitude to drug use' from successive Labour and Tory governments 'has been driven by fear rather than evidence'.

The party's cannabis plan would be informed by legalisation models implemented in Canada and some states in the US.

The manifesto also commits to 'divert people arrested for possession of drugs for personal use into treatment' rather than sending them to prison.

The Lib Dems were riding high on 23 per cent in a YouGov poll at the start of October but the party has been sinking ever since with the latest survey giving it a support rating of just 15 per cent.

Ms Swinson attempted to get her party back on track as she unveiled her 100-page blueprint for Britain and launched a stinging attack on Boris Johnson.

The Lib Dem leader criticised the Prime Minister and told activists at a campaign rally in London: 'Boris Johnson only cares about Boris Johnson.'

However, she conceded today that she is unlikely to win the election as she said such a result would require a 'big step' from where the polls are currently.

But she insisted 'it is certainly possible' that she could still win a majority and become PM.

Cancelling the UK's departure from the European Union forms the centre-piece of the party's December 12 offer to voters as it seeks to win over people who backed Remain at the 2016 Brexit referendum.

Ms Swinson is committing to spending a £50 billion so-called 'Remain Bonus' on boosting public services if the party succeeds in stopping Brexit.

Jo Swinson launched her party's election manifesto today at an event in London as she tries to stop the Lib Dems' slide in the polls

The Lib Dems argue that staying in the EU would enable the UK economy to grow faster than it would under Brexit, leading to more money being available to the government to spend on its priorities.

Lib Dem general election manifesto pledges at a glance Stop Brexit and invest a £50 billion 'Remain Bonus' in public services Legalise cannabis for over-18s Put up taxes on frequent international flyers Boost school funding by £10bn a year and recruit 20,000 new teachers Increase starting salaries for teachers to £30,000 Make 80 per cent of UK electricity from renewable energy sources by 2030 Give every adult £10,000 to spend on training and skills over the course of their lives Spend £15 billion retrofitting 26 million homes to raise energy efficiency Double solar and wind power production by 2030 Scrap the UK's continuous at-sea nuclear deterrent but maintain a downgraded capability Replace business rates in England with a Commercial Landowner Levy Build at least 100,000 homes for social rent every year Increase total house building to 300,000 a year Advertisement

Ms Swinson said that if the Lib Dems win the election and she becomes prime minister she would revoke Article 50 on 'day one' as she also suggested the decision to scrap Brexit could be communicated to Brussels 'by email'.

Ms Swinson said the party's manifesto represented a 'bold plan to build a brighter future for our country, and that starts with stopping Brexit'.

'Labour and the Conservatives can't offer the country a brighter future because they both want Brexit,' she said.

'We know that will be bad for our economy, bad for our NHS and bad for our environment.'

She added: 'Our politics has been dominated by the two, tired old parties for too long.

'This election provides an opportunity to change the future of our country and build a brighter future with the Liberal Democrats.'

Ms Swinson took repeated swipes at Mr Johnson and Jeremy Corbyn as she set out her vision for the UK at tonight's event after the party published its manifesto in full at lunchtime.

She said that both leaders were 'gambling with your future' because of their respective approaches to Brexit.

But she saved her most vicious barbs for Mr Johnson as she said: 'Boris Johnson is collecting quite the set of celebrity endorsements.

'Britain's biggest racist Tommy Robinson has come out in his support just days after Boris Johnson struck a deal with Nigel Farage.

'But at least President Trump will be happy. His two friends coming together like he wanted. Clearly President Trump's wish is Boris Johnson's command.'

She added: 'Boris Johnson only cares about Boris Johnson.'

Ms Swinson has made stopping Brexit her party's main election policy but the Lib Dem manifesto also has a heavy focus on tackling climate change

Ms Swinson had started the day with a campaign trail trip to a primary school in Cambridge

The party's manifesto is also heavy on proposals designed to tackle climate change.

The Lib Dems are committing to hiking taxes on people who frequently take international flights while reducing costs for those who only fly once or twice per year.

The manifesto pledges to: 'Reduce the climate impact of flying by reforming the taxation of international flights to focus on those who fly the most, while reducing costs for those who take one or two international return flights per year.'

It also proposes a 'moratorium on the development of new runways' in the UK and sets out opposition to expansion of existing major airports.

Meanwhile, the party said a Lib Dem government will generate 80 per cent of Britain's electricity from renewable sources by 2030.

The manifesto also contains a promise to provide free childcare from the age of nine months, to give every adult £10,000 to spend on skills and training throughout their lives and to recruit 20,000 new teachers as part of an extra £10 billion a year investment plan for schools.