Boris Johnson, the frontrunner in the race to replace Theresa May as Prime Minister, and his contender UK foreign secretary Jeremy Hunt, have both failed to completely rule out the prospect of a no-deal Brexit to meet the October 31 deadline for the UK to leave the 28-member economic bloc.
The 67-year-old structural biologist, who as President of the UK's Royal Society is the country's key advocate for science, has made a number of interventions on the subject, with the latest one directed in separate letters to both Johnson and Hunt.
"A no-deal Brexit would be bad for UK science. It would discourage recruitment of international talent, shut us out of valuable scientific collaborations, and restrict access to new medicines and technologies that benefit everyone living in the UK," Ramakrishnan writes.
"A no-deal Brexit would also restrict the UK's access to new medicines and technologies and our ability to tackle global problems, as regulatory and governance systems fall apart. It appears that little consideration is being given to the actual, real world, impacts of a no-deal Brexit on research and innovation," he says.
Ramakrishnan, who was knighted by Queen Elizabeth II in 2012 for his contribution to science, laid out facts and figures in support of his argument, highlighting that one in six academic staff in UK Higher Education Institutions was from other European Union (EU) countries.
New research commissioned by the Royal Society shows that more than a third of UK research papers are co-authored with the EU, compared for example with 17.6 per cent co-authored with the US.
"A no-deal Brexit will make the UK much less attractive. Science is increasingly an internationally collaborative endeavour and the UK's collaboration rates are increasing fastest with our European neighbours. Loss of support for UK researchers and SMEs would have an immediate impact on research and innovation already underway in the UK," he warns.
"It will take years to develop alternatives and stop valuable research in its tracks. A no-deal Brexit would also restrict the UK's access to new medicines and technologies and our ability to tackle global problems, as regulatory and governance systems fall apart," Ramakrishnan writes.
His warning this week, ahead of the winning Prime Minister candidate set to be announced next Tuesday, came as the Royal Society also released a comparative visa analysis to highlight the UK's extremely high visa costs for skilled professionals and students, which are making the country less attractive to global talent in comparison with other international science destinations.
The UK must choose an approach to immigration that enhances our science base and drives our economy, jobs and international competitiveness, notes the Royal Society as part of the analysis which finds the UK over 400 per cent more expensive in its skilled work permits.
"The UK's current offer to international talent is simply not competitive enough to guarantee our position among the leading science nations and we risk losing out as a result," said Ramakrishnan, who has consistently called for a more "sensible" post-Brexit immigration policy.
Born in Tamil Nadu, Ramakrishnan shared the 2009 Nobel Prize in Chemistry with Thomas A Steitz and Ada Yonath "for studies of the structure and function of the ribosome".