Image copyright Getty Images Image caption Natalie Bennett: "The Green Party wants to double public spending on research"

A pledge by the Greens to bring science funding up to 1% of GDP stands out from the statements offered by six party leaders about science and engineering.

So says the Campaign for Science and Engineering (Case), which asked parties with at least one sitting MP for their views ahead of the UK election.

The organisation received six letters,

David Cameron and Ed Miliband both said science was important to Conservative and Labour plans, respectively, for stimulating economic growth.

But Case said neither of the two major parties had put a firm number on that assurance.

The Conservatives have said such an announcement would have to wait until a Comprehensive Spending Review, while Labour have similarly deferred a specific commitment until its proposed "Zero-Based Review" - both of which come after the general election.

By contrast, Greens leader Natalie Bennett wrote that her party "wants to double public spending on research over the next 10 years, reaching 1% of GDP".

Although protected as a "flat cash" sum since 2010, the UK science budget has dropped in real terms and in 2012 it fell below 0.5% of GDP, according to a recent analysis. As a proportion of GDP, the nation's science spend is the lowest in the G8.

Top science organisations and their leaders have warned that this needs to be addressed, and called for the 1% public spend in a report released in February.

Despite the Greens' position as a minor party with just one MP, Case's acting director Naomi Weir said their commitment to that same figure was noteworthy.

"They're the ones who have been the most clear in describing policies that have actual numbers and commitments backing them," Ms Weir told the BBC.

Labour and the Conservatives are being "much more reserved than they were in 2010", she added.

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Analysis: David Shukman, BBC science editor

How much of last night's TV grilling of David Cameron and Ed Miliband was devoted to science and engineering?

None.

Did anyone even mention them despite all the major parties describing research and innovation as being vital for future prosperity?

No.

In the cut and thrust ahead of the election, the economy and the NHS and immigration are commanding attention - and the world of British science is struggling to make its voice heard.

The argument is simple enough: that although Britain punches well above its weight as measured by Nobel Prizes and research papers and academic citations, it is falling behind its global competitors in terms of how much they spend.

The numbers speak for themselves: Britain devotes less of its GDP to R&D than the United States and Germany and far less than that innovation powerhouse South Korea. The latest figures show it even falls below the average of the 28 members of the European Union.

Prominent figures in science all say they get a sympathetic hearing from politicians and that things could be far worse. But they also realise that while the coming weeks present an opportunity to make a case for a big increase in the spending commitment, it will be tough work even getting noticed.

Letters were also received from representatives of Plaid Cymru and the Alliance Party, as well as the Scottish government, on behalf of the SNP.

Plaid Cymru and Alliance said they would push to strengthen investment in research within Wales and Northern Ireland respectively. The SNP letter said that science and engineering are "key to achieving the overall goal of creating a more successful Scotland".

Neither the Liberal Democrats nor UKIP have responded with a letter, though Ms Weir said both these parties had been in contact with Case and demonstrated an interest in science.

"They do have something to say, but we don't yet have a letter from them," she said.

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