The British economy could overtake Germany to become the biggest in Europe within 20 years, Nick Clegg claims today.

The Lib Dem leader claims that under his plans the UK can become the 'powerhouse of Europe'.

He will call for the science budget to be protected from cuts and the the amount of public money spent on innovation to be doubled.

Official figures suggest Britain overtook France last year to become the second largest economy in Europe

Official figures suggest Britain overtook France last year to become the second largest economy in Europe.

According to Eurostat, the UK economy in 2014 hit €2.22trillion, ahead of France's €2.14trillian but well behind Germany's €2.9trillion.

The Centre for Economic and Business Research has predicted that within the next two decades, Germany, held back by a declining population and the weakness of the euro, could be overtaken by the UK for the first time since 1954.

At an event at London's docklands, Mr Clegg will set out an ambition to sustain economic growth of an average of more than 1 per cent higher per year than Germany until 2035.

Lib Dem leader Nick Clegg claims that under his plans the UK can become the 'powerhouse of Europe'

The plan will involve ring-fencing the £4.6 billion science budget, with a commitment to increasing it in real terms once the deficit is eliminated.

The party's manifesto will also commit to doubling innovation spending across the economy, increasing the Government contribution in real terms by 2020-21 from £454 million in 2014-15 to more than £1 billion.

Mr Clegg will say: 'The Liberal Democrats have rescued the economy and led the recovery. Now is the time to be ambitious about our future.

'We believe that by building a strong, modern, open economy we can become the powerhouse of Europe. We can grow faster than both France and Germany, overtaking them as the largest economy in Europe in 20 years' time.

'That is hugely ambitious but absolutely possible. To do it we need two things: to secure the recovery; and to put in place an ambitious long-term plan that harnesses and encourages the skills and dynamism of British workers and British businesses.'

Experts say Germany is being held back by a declining population and the impact of the eurozone crisis which continues to dog the single currency.

Business Secretary Vince Cable will use today's event to highlight his commitment to the European Union and encouraging international students to come to the UK - both issues the Lib Dems have clashed with the Conservatives over in government.

Mr Cable will say: 'In Government, the Liberal Democrats have enacted important reforms to move Britain away from a culture of short-termism to one where business and government thinks long-term beyond the political cycle.

'Our industrial strategy has laid the foundations to give business the confidence to invest over a number of years by planning for the provision of skills, finance and innovation.

'The Liberal Democrats are on the side of business in creating an economy that is open to international students and the global skills pool our country needs to grow. Britain has thrived by being part of the European Union and that is why the Liberal Democrats remain committed to ensuring we continue to play our part in the world's largest single market.